Coincidences happen every day, but when they become part of the historical record, they take on a whole new meaning. From the intersection of John Adams and Thomas Jeffersons deaths to a novelist writing the story of the Titanic two decades before it sank, American history is full of coincidences so unlikely some have even given rise to conspiracy theories.1. Thomas Jefferson and John Adams Died on the Same DayLeaders of the Continental CongressJohn Adams, Morris, Hamilton, Jefferson, by A. Tholey, 1894. Source: Library of CongressJuly 4 is known to Americans as Independence Day, but it also marked the day that Thomas Jefferson and John Adams died within hours of each other in 1826.Jefferson and Adams had a tumultuous relationship with ups and downs over their lifetimes. The two men first met and became friends in 1775 when the Continental Congress convened for the first time. Their teamwork in drafting the Declaration of Independence brought them closer, but that relationship would sour when Jefferson beat Adams to become president in 1801. Jefferson identified as a Republican, and Adams as a Federalist. They stayed estranged for nearly a decade.In 1812, however, nearly 40 years after the United States became a nation, Jefferson and Adams rekindled their friendship and remained friends for nearly 15 years. This reversal took Jeffersons retirement from the presidency in 1809, the intervention of a mutual friend by the name of Dr. Benjamin Rush, and an admission by Adams. A neighbor of Jeffersons visited Adams and heard him say, I always loved Jefferson, and still love him. The neighbor then reported back to Jefferson, who asked Dr. Rush to urge Adams to renew their exchange of letters. Finally, Jefferson and Adams began to write to each other again about both political and personal issues of the past, present, and future.By 1826, both men had entered their twilight years; Jefferson was 83, and Adams was 90, so each had lived a long life. On the 50th anniversary of the birth of the nation, Jefferson died at his home in Monticello just after lunchtime. Adams followed soon after, passing away in Massachusetts just hours later. Though it is common knowledge today that Jefferson and Adams both died on July 4, 1826, at the time, breaking news traveled much slower than it does today. Neither man knew of the others death, nor did the nation until some time later.2. The Civil War Started and Ended on Wilmer McLeans PropertyUndated photograph of Appomattox Courthouse, Appomattox County, VA. Source: Library of CongressHow many Americans can say that their property bookended the deadliest war fought on American soil? The answer is exactly one: Wilmer McLean.The Civil War began on July 18, 1861, when a cannonball exploded through a house owned by McLean. McLean, however, was not the target of the attack, which had been commandeered by Confederate General Pierre Gustave Toutant-Beauregard. This sudden attack began what is today called the Battle of Bull Run. Despite the battle taking place so close to home, McLean was still happy to host Beauregard because McLean himself was a retired militia officer and felt a sense of duty to the General. By August 1862, the Second Battle of Bull Run began on the same property, and McLean, unhappy with the violence and danger, finally moved his family to southern Virginia.From 1862 to 1865, the McLean family knew peaceuntil Robert E. Lees aide, Charles Marshall, approached McLean in early April of 1865. Marshall was looking for a location for two generals to meet, and yet again, McLean reluctantly offered his home to the cause. Thus, on April 9, 1865, Robert E. Lee met another general by the name of Ulysses S. Grant for the purpose of surrendering the Confederate Army, thus ending the Civil War. After a short conversation on the warm afternoon of April 9, the Civil War ended in McLeans Appomattox Court House home, just under four years after it had begun in his previous Manassas home.3. Halleys Comet Marked Mark Twains Birth and DeathMark Twain, three-quarter length portrait, seated, facing slightly right, with cigar in hand, by A.F. Bradley, 1907. Source: Library of CongressMark Twain, born Samuel Langhorne Clemens, was born on November 30, 1835. Twain is best known for his novels The Adventures of Tom Sawyer and Adventures of Huckleberry Finn, but his travel literature was quite popular with American audiences as well. The authors birthday was marked by a once-in-a-lifetime astronomical event. Twains birth came just two weeks after Halleys Comet passed by Earth in 1835.Halleys Comet passes Earth every 75 years, give or take, which means most people will only have one opportunity to view Halleys Comet in their lifetime. Halleys Comet is also an important astronomical discovery because it was the first comet that scientists realized could pass by Earth more than once. By the time Halleys Comet passed in 1835, scientists had known for over 100 years that the comet had visited in 1531, 1607, and 1682. The comet and following meteor showers were the same comet, not different ones each time. Indeed, scientists can trace observations of the comet back over 2,000 years.This, taken on its own, is an interesting fact but nothing groundbreakinguntil you learn what passed again before Twain died. In 1909, Twain commented on Halleys Comet, saying, [We] came in together, [we] must go out together. One year later, Twain died on April 21, 1910, just one day after Halleys Comet again passed Earth on April 20. Twain indeed both came in and went out with Halleys Comet.4. The Tale of Two JimsTwins separated at birth, Jim Springer and Jim Lewis. Source: RipleysMany people, at least once, have wondered what it might be like to be reunited with a long-lost twin. Some anticipate seeing the matching physical characteristics, such as hair and eye color. Others go further and wonder if their estranged twin would have the same medical conditions, if they also wore glasses, if they were also right- or left-handed. What happens when that daydream actually comes trueand not only that, but you realize you and your long-lost twin have lived nearly identical lives?A pair of twins born in 1940 spent just four weeks together before being adopted by two different Ohio families. However, when twins James Arthur Springer and James Edward Lewistheir matching names just a hint at their similaritieswere reunited in 1979, the overlap between their lives, despite growing up in different families and environments, was shocking.The Jims shared surprising similarities, including marrying and divorcing a woman named Linda, taking a second wife named Betty, naming their childhood dog Toy, growing up with an adopted brother named Larry, vacationing at the same beach in Florida, and working as part-time deputy sheriffs in Ohio.Coincidences did not stop with the twins themselves either; they spilled over to their families, too. Springer named his son James Allan, while Lewis named his son James Alan. It seems that the Jim twins could not have led more identical lifestyles, even if they had grown up together.5. Morgan Robertson Predicted the Titanic SinkingTITANIC, to be launched, unknown photographer, 1911. Source: Library of CongressIn 1898, American author Morgan Robertson published a novel called Futility, or The Wreck of the Titan. Robertson spun the tale of a ship called the Titan that had three fantastic qualities: it is the worlds longest, fastest, and only unsinkable ship. Unfortunately, the ship collides with an iceberg on its maiden voyage, splits in two, and sinks in the middle of the ocean. Over 2,000 passengers lost their lives because there were not enough lifeboats.Sound eerily familiar? Indeed, nearly two decades before the unsinkable Titanic sank in 1912, Robertson published the grim tale of the worlds most impressive ship sinking after a collision with an iceberg. Here are a few more qualities that the fictional Titan and real-life Titanic shared:Both ships were about 800 feet longEach ship weighed roughly 70,000 tons and used triple-screw propellers to moveCapacity on both ships was 3,000 passengersRich individuals from both U.S. and European high society were aboardBoth ships sank in AprilCover of Robert Morgansons novel Futility. Source: Royal Museums GreenwichSave for the conspiracy that Robertson was a time traveler who witnessed the sinking of the Titanic, there is no explanation for the similarities between the fictional and real tragedies. One of the most likely explanations behind Robertsons harrowing tale would have been an interest in sailing and maritime technological developmentsalongside the authors impressive creativity and storytelling.