15 The Chinese Empire ended in the same decade that the first commercial radio signal became available.

The first radio signal became commercially available in the early 1920s following the First World War. This was only about ten years after the Qing Dynasty, the last imperial dynasty of China, came to an end in 1912, after having ruled for more than 250 years.(1,2)

16  Thomas Jefferson and John Adams died five hours apart on July 4, 1826.

Thomas Jefferson and John Adams, former presidents of the United States of America and two of the last surviving revolutionaries, died on the same day within five hours of each other. Jefferson, then eighty-two, died before Adams, who was ninety at the time of his death.(source)

17 Queen Elizabeth and Marilyn Monroe were born in the same year.

Queen Elizabeth II was born on April 21, 1926, in London. About two months later, Norma Jeane Mortenson, who later went by the name Marilyn Monroe, was born half a world away on June 1, 1926, in Los Angeles.(1,2)

18 Charlie Chaplin and Hitler were born in the same year.

Charlie Chaplin is older than Adolf Hitler by four days. Chaplin was born on April 16, 1889, while Hitler was born on April 20, 1889. Interestingly, Chaplin also satirized Hitler in his film The Great Dictator.(1,2)

19 Yellowstone National Park is only about a year younger than Germany.

The Yellowstone National Park in the U.S.A. was established in 1872, a year after the German Empire was founded at Versailles which united all parts of Germany except Austria.(1,2)

20 Abraham Lincoln was assassinated a few months before the formation of the Secret Service.

The U.S. Secret Service was formed on July 5, 1865, three months after then-President Abraham Lincoln was assassinated by John Wilkes Booth on April 15, 1865. Interestingly, Lincoln had established the Secret Service the same day that he was shot.(source)

21 The Titanic sank the same year that Oreos were introduced in America.

RMS Titanic sank on its maiden voyage in April of 1912 in the Atlantic Ocean after hitting an iceberg, just a month after Oreo cookies were introduced in America.(source)