The Manhattan Project is famously known as the United States-led endeavor which successfully created the first atomic bomb. The success of the Manhattan Project led to the bombings of Nagasaki and Hiroshima in 1945 and the total surrender of Japan, ending World War II.

The project was extremely complex and dangerous, even causing the deaths of some of its own scientists. Nevertheless, its story is fascinating, and it is one of the most significant human achievements in the history of our world. Our list today looks at ten interesting facts from the Manhattan Project and the people who helped to make it happen.

10 Einstein Was Integral To The Project Happening

The history of the Manhattan Project is often told as beginning with the Einstein-Szilard letter. This famous letter, which was signed by Albert Einstein himself in 1939, was mailed to the president of the United States, Franklin D. Roosevelt. The writer of the letter, Leo Szilard, had composed it in conjunction with other prominent physicists Eugene Wigner and Edward Teller, based on the realization that a new power was emerging from the nuclear research of the time. This power, harnessed by heavy atoms, could cause destruction unlike anything the world had seen before, and this was a potentially extremely dangerous position to be in, as Nazi Germany could harness this power.

Szilard organized getting the letter composed with Einstein, and it was sent to President Roosevelt. The letter said, “This new phenomenon would also lead to the construction of bombs,” and that this “could be achieved in the immediate future.”^[1] The letter also said that Germany had already begun to stockpile sources of uranium from Czechoslovakia, suggesting that the Nazis were already researching the new science. Roosevelt received the letter and decided to take action, creating the Advisory Committee on Uranium. This was the very beginning of the US government supporting research into uranium and would ultimately lead to the Manhattan Project, which started in 1942.

9 The Project Was Infiltrated By Russia

The Manhattan Project was, for obvious reasons, top secret, and intelligence officials and the FBI did everything they could to keep Nazi Germany or Japan from learning about what was happening. Although the USSR were allies of the US, the US still wanted to keep them away from the project and avoid them benefiting from the research and testing being conducted. Despite this, the USSR managed to successfully infiltrate the Manhattan Project. Soviet intelligence had picked up on the fact that British and American publications into nuclear fission had recently dipped—this was a red flag.

Reportedly, Soviet spies were foiled at many attempts, but some managed to infiltrate the project and send back critical information—one of the most notable being Klaus Fuchs. Fuchs, a physicist, had secretly sworn allegiance to the USSR, offering his services to them. He had been assigned to the Los Alamos laboratory working on bomb research and design. He would pass on information to the USSR while working in Los Alamos and would be eventually caught after the war, confessing to everything.^[2] Other spies remain unknown to this day, and their identities were never uncovered by US counterintelligence.

8 The Project Cost Almost $2 Billion

The Manhattan Project was a complex effort, spread out over multiple sites across the US and Canada. The most important sites to the project were Oak Ridge in Tennessee and Los Alamos in New Mexico. Oak Ridge served as the main production plant, which produced the enriched uranium needed to create an atomic bomb. The Los Alamos site was a remotely located laboratory which was tasked with designing and building the bombs.^[3] The first-ever detonation of a nuclear bomb in history was achieved in New Mexico, when the Trinity test was performed.

Many other sites fed into the project, and because of this, the costs added up. Much of the expense came from the Oak Ridge site. It was estimated that the total project costs were $1.9 billion, which would be well over $20 billion in today’s dollars.

7 The Project Was Deemed A Success

Despite the costs of the project being more than originally budgeted, despite the fatalities during the work, and despite all of the scientific challenges that occurred, the Manhattan Project was deemed a success. The overall objective of the project was to arm the US with an atomic bomb against the Nazi or Japanese threat of doing the same. However, whether the project really was a success is more of an ethical question than a factual one. The project delivered the only two atomic bombs ever detonated in warfare, with the total estimated deaths from those detonations being somewhere between 150,000 and 200,000 people.^[4]

The bombs ushered in a new nuclear era in which Russia and the US would emerge as superpowers, both armed with nuclear bombs, ready to destroy entire cities instantly. The bombings in Japan in 1945 brought about an abrupt end to the war and potentially saved many US lives, but the bombings today still pose a problematic question as to whether they were truly necessary and if they were morally correct. Some would argue they were a war crime; others would say they were justified and necessary. Without the “success” of the Manhattan Project, who knows who would have been the first country to use a nuclear bomb in World War II?

6 The Demon Core

According to reports, there were 24 fatalities during the Manhattan Project’s lifespan. Many of these were deaths caused by things like construction accidents. However, for scientists Harry Daghlian and Louis Slotin, it was a different case completely. Daghlian was a scientist who was working on experiments using the third nuclear core (with the first and second having been used in Japan). On August 21, 1945, Daghlian accidentally dropped a tungsten carbide brick onto the plutonium core assembly, which made the core go supercritical. He quickly got the brick off the core, but he would receive a lethal dose of radiation because of his accident and died in agony around a month later.

Despite this incident, nine months later, Slotin would die from the same core in another fatal accident. On May 21, 1946, Slotin was holding the top part of a beryllium neutron reflector in place above the core assembly with a screwdriver. (A recreation of the procedure is pictured above.) Then, his screwdriver slipped, and the half-sphere fell totally onto the core. This slip caused a lethal amount of radiation to be released in a flash of blue light. Slotin quickly flipped the top part of the reflector off the core and onto the floor, neutralizing the threat. Nevertheless, the he would die from acute radiation poisoning nine days later.^[5]

The plutonium core was later nicknamed the “Demon Core” because of its involvement in the two scientists’ deaths. It was later melted down, and its material was used in other cores.

5 Thin Man

In the early stages of the Manhattan Project, considerable research and attention was placed on designing a plutonium-based “gun-type” bomb. The work was code-named “Thin Man,” in contrast to the “Fat Man” bomb dropped on Nagasaki. Fat Man worked by plutonium implosion, whereas Thin Man bombs would have worked by having two plutonium masses coming into contact with each other at high speed inside the bomb.

Thin Man was ultimately abandoned due to a number of difficulties experienced during research. Firstly, the bombs would have been 5.2 meters (17 ft) long, and this posed a challenge, as finding a suitable aircraft to carry them was difficult. Bombers could be modified to fit the longer casings, but it was later learned that the design of the two plutonium masses made the bombs likely to pre-detonate. Due to this, the casings would have to have been extended, and this put the design outside the realms of what was possible to carry on an airplane of the time.^[6] This effectively spelled the end of the project. “Little Boy,” the bomb ultimately dropped on Hiroshima, was a gun-type bomb, but it utilized uranium-235 instead of plutonium-239, as Thin Man bombs would have.

4 The Trinity Test Had Provisions In Case Of Disaster

One of the key milestones of the Manhattan Project was the Trinity test—the first-ever detonation of a nuclear bomb. The test occurred on July 16, 1945, and was conducted by exploding “Gadget,” a device similar to Fat Man. The test was successful and quite literally started the atomic era.

Prior to the test, which was top secret, officials were forced to come up with ways to hide it from the public and press, which would prove difficult, considering the enormity of the predicted explosion. A writer for The New York Times, William Laurence, had been drafted into the Manhattan Project for this very reason. Laurence would help put together press releases that would cover up the events. Laurence wrote four press releases for the public attention the test would garner, with the most severe including a blank list of those people killed by the explosion and instructions for evacuation situations.

There was considerable worry that this press release would be needed. However, the press release ultimately used hid the event by attributing the noise and heat wave to a “remotely located ammunition magazine containing a considerable amount of high explosives and pyrotechnics” that had exploded.^[7]

3 The Project Was Not Based In Manhattan

Despite the name of the Manhattan Project, the bulk of the work conducted during its existence didn’t take place in Manhattan. In fact, as mentioned, the two most prominent sites were in New Mexico and Tennessee. During the project’s beginning, its official name was “Development of Substitute Materials,” but this never really stuck. President Roosevelt had assigned the project to the Army, and General Leslie R. Groves took up residence in Manhattan initially to draw on the nearby Corps of Engineers division.^[8]

Later, it was agreed that “Development of Substitute Materials” may have been too obvious, so they settled for “Manhattan District.” As the project expanded, and the need for multiple sites and laboratories became evident, the Army began to move away from Manhattan. However, the name followed them. Later on, the “District” part was used less and less until the project was known simply as the “Manhattan Project.”

2 The Doomsday Clock Was Born Out Of The Manhattan Project

After the closure of the Manhattan Project, many scientists were left ruminating about the overall impact the nuclear bomb would have in the future of the Earth. After the bombings of Nagasaki and Hiroshima, it’s not hard to see why. Therefore, in 1945, the Bulletin of the Atomic Scientists was created, and it began to publish monthly informational pieces about the developments and dangers of the newly dubbed “Atomic era.”^[9] One of the founders of the Bulletin was a biophysicist named Eugene Rabinowitch, who had worked on the Manhattan Project during World War II. Rabinowitch said that the aim of the Bulletin was to “awaken the public to the full understanding of the horrendous reality of nuclear weapons and of their far-reaching implications for the future of mankind.”

In 1947, the Bulletin started to produce the Doomsday Clock, a way of measuring how close humanity was to destroying the world with man-made nuclear weapons. When the first Doomsday Clock was released, the time was 11:53 PM (seven minutes to midnight). The furthest away the clock has been from midnight was in 1991, at the end of the Cold War between Russia and the US. The clock is presently at two minutes to midnight, the worst it has ever been, due to current concerning international stances of countries.

1 The Project Is Still Referenced In Popular Culture Today

The Manhattan Project has certainly not been forgotten more than 70 years after its completion. It is still referenced in many popular culture genres, essentially paving the way for an entirely new subgenre of nuclear destruction. The Manhattan Project has been featured in many television shows, movies, documentaries, pieces of fiction, music, art, and other forms of pop culture such as video gaming and board games.

Quickly following the close of the project, the film The Beginning or the End was released in 1947, which depicted an inaccurate and villainous story of how the atomic bombs were made.^[10] Many years later, the TV movie Day One provided a much more accurate portrayal of the project, going on to win an Emmy Award for Outstanding Drama. More recently, the Manhattan Project has been referenced in the Marvel Cinematic Universe in Iron Man, where the central character Tony Stark makes reference to his father helping the Manhattan Project.

Other portrayals include books such as Los Alamos by Joseph Kanon and The Wives of Los Alamos by Tarashea Nesbit. In 2014, a television series simply named Manhattan was produced for two seasons to critical acclaim before its cancellation in 2016. There have been and will continue to be many depictions of the project, as over 70 years later, we still find ourselves fascinated by the work conducted during the Manhattan Project.

New York City’s modernity makes it difficult to imagine a time when it was anything but a land of skyscrapers, subways, and gridlock. But its origins are indeed humble. To properly explore the city’s roots, one must start with its nexus: Lower Manhattan.

NYC was built from the southern tip up. A walking tour of Lower Manhattan is refreshingly rambling as its narrow streets predate the grid system imposed on the remainder of the island starting in the early 1800s. Consider the following a best-of history guide for the next time you’re in the Big Apple.

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10 Collect Pond

The area currently occupied by Chinatown’s Columbus Park sits atop what was once Lower Manhattan’s primary source of fresh water: the (eventually) aptly named Collect Pond.

Before the Europeans, the Lenape Native Americans had a settlement along its shoreline. In the 1540s, the French established a fortified trading post on one of its lush islands. Starting in the early 18th century, the British used the pond alternately as a summer picnic spot and a winter skating rink.

Around this time, however, Collect Pond took a turn for the . . . well, gross. A number of tanneries moved into the area. (Mulberry Street, which overlooked the pond, became known as “Slaughterhouse Street.”) By the 1800s, Collect Pond had collected enough waste that it was deemed “a very sink and common sewer.”^[1]

In 1807, the city started construction on a canal—modern-day Canal Street—that would funnel the polluted water into the Hudson River. A hasty drainage job left a marshy, mosquito-ridden landfill upon which wealthy slumlords built tenements for the poor, including many newly arriving immigrants.

9 The Five Points Slums

Built partially on land filled in over fetid Collect Pond and famously depicted in Martin Scorsese’s epic 2002 film Gangs of New York, The Five Points was loosely bound by Centre Street to the west, the Bowery to the east, Canal Street to the north, and Park Row to the south.

The neighborhood’s name derives from a starlike confluence of two crossing streets and a third that terminates at their intersection, forming “points.” Those thoroughfares were Anthony Street (now Worth), Cross Street (now Mosco), and Orange Street (now Baxter). This guide^[2] shows its approximate location today.

The Five Points was the filthiest, most congested district in an already flighty, overcrowded Lower Manhattan. Living conditions were crammed and squalid. Shoddily constructed tenements on unstable, poorly drained ground quickly became dilapidated.

The unsanitary, overpopulated conditions became breeding grounds for cholera, tuberculosis, typhus, malaria, and yellow fever. Worse, the problem fed upon itself as hundreds of thousands of overwhelmingly poor immigrants poured into New York annually, providing slumlords with a steady stream of desperate souls to exploit.

Crime, organized and otherwise, was rampant. For most of the 19th century, The Five Points is alleged to have had the highest murder rate of any slum in the world. Prostitution and gambling reigned, including the gentlemanly sport of rat fighting.

The Five Points and adjacent Lower East Side served as the backdrop for James Riis’s mesmerizing 1890 book How the Other Half Lives, which paved the way for safety, sanitation, and economic reforms throughout Lower Manhattan.

8 Castle Clinton

Before Ellis Island, there was Castle Clinton, the nation’s first official immigration processing center. The castle was first constructed due to the growing tensions between the United States and Britain in the early 19th century. The 28-cannon fort, which was garrisoned but never saw action during the ensuing War of 1812, occupied what was then an artificial island off Manhattan’s southern tip.

The locale has a dark legacy. After the Lenape Native Americans refused to pay Dutch settlers taxes in the 1640s, the governor decided that a fitting penalty was slaughtering every man, woman, and child . . . and decorating Castle Clinton’s predecessor, Fort Amsterdam, with their heads.^[3]

The castle received its current name in 1815 in honor of outgoing NYC Mayor DeWitt Clinton. Upon becoming state governor, he led the effort to build the Erie Canal, a 584-kilometer (363 mi) engineering marvel connecting the Great Lakes to the Atlantic Ocean via New York’s Hudson River.

No longer a military necessity, Castle Clinton became, in turn, a beer garden, exhibition hall, opera house, and theater before transitioning to an immigration center in 1855. It remained in this role until 1890. Then the immigration center was moved to Ellis Island.

True to the Castle Clinton’s Lower Manhattan roots, many immigrants were cheated out of their possessions by corrupt workers, and some even died awaiting entry into the US. Its island now filled in and connected to the mainland, Clinton Castle still stands today at the southern endpoint of (what else) Bridge Street. Tours are readily available.

7 Fraunces Tavern

Up for a pint? Duck into the oldest bar in New York City: Fraunces Tavern at 54 Pearl Street.

Constructed in 1719, the watering hole carries the name of Samuel Fraunces, who operated the establishment as the Queen’s Head Tavern during the 18th century. During the Revolutionary War, Fraunces and his tavern were part of a spy ring undermining the British occupation of New York. (The British held New York for nearly the entire war, necessitating an intricate web of espionage and sabotage terrifically depicted in the TV series TURN: Washington’s Spies.)

Following the cessation of hostilities, George Washington held a farewell party at the tavern for high-ranking Continental Army officers. The joint also undoubtedly had its share of revelers on November 25, 1783, when the British formally departed the former colonies from nearby Evacuation Day Plaza.

In 1789, Fraunces became newly inaugurated President George Washington’s first chief steward, overseeing the head of state’s household affairs. Fraunces died in 1795 while Washington was still in office.

In recent years, Fraunces has become the center of a new controversy: his race. After being portrayed as white for centuries, many historians now believe he was a (free) black man.^[4]

In addition to operating as a bar and restaurant, Fraunces Tavern now features a museum dedicated to Lower Manhattan’s Revolutionary War era.

6 The African Slave Trade And Burial Grounds

Although slavery is typically more associated with the US South, New York City was the second-largest slave-owning city in the British colonies in America in the mid-18th century. (Charleston, South Carolina, was the biggest.)

Ironically (and tragically), most of the macabre buying and selling of human beings transpired at a street now synonymous with commerce: Wall Street. At 74 Wall Street, a 42-story building housing luxury condominiums rests over what was once New York’s primary slave market.

The “peculiar institution’s” history in New York is as old as the city itself. The first slaves arrived in New Amsterdam in 1626, just two years after the Dutch settled there. Slave labor was instrumental in building defensive structures for the small, vulnerable European population—including the wall for which the modern street is named.^[5]

Today, the only remaining evidence of the slave market is a plaque erected in 2015. However, nearby is the African Burial Ground Memorial, the oldest and largest known excavated burial ground in North America for persons of African origin. Unsurprisingly, blacks were not permitted to be buried in cemeteries alongside whites. Deceased African Americans, both free and enslaved, were relegated to mass gravesites.

The memorial sits atop a site that went undiscovered until 1989, when preconstruction activities for a federal office tower found some 15,000 skeletons dating from the 1630s through the 1790s. Slavery was not outlawed in New York State until 1827.

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5 City Hall Park

The grassy grounds surrounding New York’s City Hall represent perhaps the only sizable patch of land in Lower Manhattan never to be fully developed. The original Dutch settlers used the area as a public commons. The space took a darker turn when the British seized the colony in 1664 and hosted public executions.^[6]

More death and despair followed. In 1775, the British began work on a prison named Bridewell. Soon, the American Revolution broke out in full force, giving the redcoats more pressing priorities than proper penitentiaries. The unfinished building—which even lacked windowpanes to protect from bitter cold winters—was a pit of suffering and death for hundreds of POWs until the war’s conclusion.

In the years immediately preceding the war, the grounds became a popular spot for “Liberty poles,” erected to inspire insurrectionist spirits and often to signal covert conventions of anti-British conspirators. An 18th-century game of whack-a-mole ensued, with pro-independence groups like the Sons of Liberty putting poles up as fast as British soldiers could chop them down.

The poles were figurative lightning rods that made bloody confrontation inevitable. In January 1770, British soldiers were attacked mid-removal by patriots. The subsequent skirmish on nearby Golden Hill, which preceded the Boston Massacre by several weeks, is where modern-day Gold Street gets its name.

Along with a stone plaque, a 20-meter-tall (66 ft) replica of the sawed-off liberty pole was installed in 1921.

4 The Catacombs At Old St. Patrick’s Cathedral

The most famous burial ground in Lower Manhattan is undoubtedly the graveyard at Trinity Church at the intersection of Wall Street and Broadway. The cramped site is the final resting place of several famous figures, most notably Alexander Hamilton.

However, another gravesite offers a much more immersive experience. At Old St. Patrick’s Church in modern-day SoHo—far humbler confines than the current polished behemoth in Midtown—visitors can tour catacombs where the city’s wealthier Catholic residents sealed themselves for all eternity.^[7]

Both the catacombs and the high wall in the adjacent church graveyard were intended to prevent something widespread in 19th-century Lower Manhattan: grave robbing. Understandably, avoiding post-death looting took some, well, loot, a price point that limited the catacombs to especially prominent New Yorkers. Several members of the Delmonico restaurant family are there, as is the man credited with bringing opera to NYC.

One interment of interest is Thomas Eckert, who served in several capacities, including presidential bodyguard, in the administration of Abraham Lincoln. On April 14, 1865, Lincoln wanted Eckert for exactly that role while he took in a play at a Washington, DC, theater. Unfortunately, Secretary of War Edwin Stanton refused permission for Eckert to go.

Allegedly, Stanton claimed that he had an important task for Eckert that night. Controversy remains about the real reason Eckert wasn’t guarding Lincoln’s viewing box when John Wilkes Booth assassinated Lincoln later that night.

3 Mob Hit Hunting In Little Italy

Despite being a shell of its former self—its footprint has been severely compacted by Chinatown from the south and Nolita from the north, and its restaurants are now mostly tourist traps—Little Italy is still a great place to see where some high-profile mafiosi got whacked.

At the famed Umberto’s Clam House at 132 Mulberry Street, Colombo crime family hit man Crazy Joe Gallo was enjoying dinner with his family, including his 10-year-old daughter. The date was April 7, 1972—Gallo’s birthday.

Sometime during his second helping of shrimp and scungilli (not a bad choice for a last meal), gunmen entered the restaurant and opened fire. The shooting marked the first time a mobster was murdered in front of his family, so he must have made someone really mad.

Another high-profile murder took place in the late 1930s at the site of the former ‘O Sole Mio restaurant, also on Mulberry Street. The grisly photo of an unidentified mob hit victim sprawled out on the street made headlines across New York. Unfortunately, the site now houses a tacky souvenir shop selling “I Heart NY” T-shirts to clueless tourists.^[8]

Slightly outside the boundary of Lower Manhattan, the Museum of the American Gangster at 80 St. Mark’s Place offers a deep dive into mob history.

2 The City’s Oldest Sites

New York is a city where the only thing constant is change. In fact, only one structure remains from the 1600s (its first century of European inhabitation): a cemetery. Coincidentally, it is the final resting place of the city’s first Jewish settlers.

In modern-day Chinatown, the site holds 107 graves with headstones that have remained surprisingly legible. The cemetery was used at least through the American Revolution as it includes the remains of several fallen soldiers.

The oldest surviving building is the aforementioned Fraunces Tavern, but many historians discount this distinction due to its series of renovations. The title of oldest original building goes to St. Paul’s Chapel, which dates to 1764. The house of worship includes a pew where George Washington prayed on the day of his presidential inauguration.

Nearby, the Edward Mooney House was completed in 1789 and has served as a private residence, hotel, brothel, and saloon over its long history. At the turn of the 20th century, it was headquarters to an odd bloke named Chuck Connors, the self-proclaimed “mayor of Chinatown.”

He led voyeuristic whites on slumming tours through the rowdy Bowery bars and Chinese opium dens. Notably, Connors once helped future legendary songwriter Irving Berlin get a waiting gig at a local restaurant.

Today, the Chinese characters adorning the building’s second-floor facade showcase the staying power of Chinatown.^[9]

1 Chinatown

Chinatown is the only substantial ethnic neighborhood remaining in Manhattan. Others like African-American Harlem, Latino Washington Heights, and especially Little Italy have long been whittled away by gentrification.

For first-time visitors, Chinatown is simultaneously inviting and intimidating. Decrepit yet delicious dumpling houses, Eastern medicine pharmacies showcasing vast rows of herbal remedies, shops brazenly peddling dubiously authentic clothing and handbags, and cavernous dim sum restaurants—including the 800-seat, soccer-pitch-sized Jing Fong—line the narrow, typically crowded streets.^[10]

Chinese immigrants began settling in Lower Manhattan in the 1870s. As Easterners in a Western world who were viewed as “others” even by other new arrivals from Ireland, Italy, and Germany, the Chinese developed a necessary insularity further exacerbated by the 1882 Chinese Exclusion Act. This limited the number of Chinese allowed to immigrate to the US.

Like other ethnic groups in 19th-century Lower Manhattan, the Chinese formed violent gangs. Known as tongs, the gangs ran opium dens, prostitution rings, and gambling halls. One narrow Chinatown alley, the elbow-shaped Doyers Street, became notorious as the “Bloody Angle” for a deadly inter-tong battle that left several gang members dead.

The killers escaped via another fascinating Chinatown anomaly: a winding series of underground tunnels used for illegal smuggling and quick getaways from law enforcement. Today, nearby Chatham Square offers the last accessible vestige of this tunnel network, known today as the Wing Fat Shopping Arcade.

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About The Author: Christopher Dale (@ChrisDaleWriter) writes on politics, society, and sobriety issues. His work has appeared in Daily Beast, NY Daily News, NY Post, and Parents.com, among other outlets.