April 25

1953: Francis Crick and James D. Watson published “Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid” describing the double helix structure of DNA.
1959: The St. Lawrence Seaway, linking the North American Great Lakes and the Atlantic Ocean, officially opened to shipping.
1974: Workers for the Dowling Construction Co. of Indianapolis left a five-ton steel wrecking ball hanging from a crane 200 feet above the ground. When they returned the next morning, the ball was gone. Police had no explanation and the ball was never found.

April 26

1564: Playwright William Shakespeare was baptized in Stratford-upon-Avon, Warwickshire, England (date of actual birth is unknown).
1965: A Rolling Stones concert in London, Ontario, was shut down by police after 15 minutes due to rioting.
1973: Actress Irene Ryan, 71, best known as “Granny” on TV’s Beverly Hillbillies, suffered a stroke while performing in the Broadway musical Pippin. (She died six weeks later.)
April 27

1667: The blind and impoverished John Milton sold the copyright of Paradise Lost for $10.
1902: J. Sterling Morton, the founder of Arbor Day, died at age 70 in Nebraska City, Neb.
1974: Ten thousand people marched in Washington, D.C., calling for the impeachment of President Richard Nixon
1981: Xerox PARC (Palo Alto Research Center Inc.) introduced the first computer mouse.
2006: Construction began on the Freedom Tower for the new World Trade Center in New York City. (The name was changed on March 30, 2009, to 1 World Trade Center.)
April 28

1932: Yellow fever vaccine was introduced.
1937: Born this day: Saddam Hussein, fifth president of Iraq (executed 2006).
2001: American Dennis Tito paid $20 million to the Russian space program and became the first paying passenger in outer space.

April 29

1992: Riots broke out in Los Angeles, Calif., following the acquittal of police officers charged with excessive force in the beating of Rodney King. Over the next three days, 53 people were killed and hundreds of buildings were destroyed.
2004: Oldsmobile built its final car, ending 107 years of production.
2011: Prince William, Duke of Cambridge, married Kate Middleton in London. She became the Duchess of Cambridge.
April 30

1789: The first inaugural ball was held in New York for President George Washington.
1803: The United States purchased the Louisiana Territory from France for $15 million, more than doubling the size of the young nation.
1927: Douglas Fairbanks and Mary Pickford became the first celebrities to leave their footprints in concrete at Grauman’s Chinese Theater in Hollywood, California.

May 1

1931: The Empire State Building in New York City was dedicated.
1956: The polio vaccine, developed by Jonas Salk, was made available to the public.
1999: The body of British climber George Mallory (“Because it’s there”) was found on Mount Everest, 75 years after his disappearance in 1924.

May 2

1611: The King James Bible was published for the first time in London, England, by printer Robert Barker.
1986: The city of Chernobyl, Ukraine, was evacuated six days after the nuclear power plant there exploded and melted down.
2000: President Bill Clinton announced that accurate GPS access would no longer be restricted to the United States military.