On this day, July 24 …

1937: The state of Alabama drops charges against four of the nine young black men accused of raping two white women in the "Scottsboro Case."

Also on this day:

1858: Republican senatorial candidate Abraham Lincoln formally challenges Democrat Stephen A. Douglas to a series of political debates; the result would be seven face-to-face encounters.

Republican senatorial candidate Abraham Lincoln formally challenges Democrat Stephen A. Douglas to a series of political debates; the result would be seven face-to-face encounters. 1866: Tennessee becomes the first state to be readmitted to the Union after the Civil War.

Tennessee becomes the first state to be readmitted to the Union after the Civil War. 1959: During a visit to Moscow, Vice President Richard Nixon engages in his famous "Kitchen Debate" with Soviet leader Nikita Khrushchev.

1969: The Apollo 11 astronauts — two of whom had been the first men to set foot on the moon — splash down safely in the Pacific.

1974: The U.S. Supreme Court unanimously rules that President Richard Nixon has to turn over subpoenaed White House tape recordings to the Watergate special prosecutor.

The U.S. Supreme Court unanimously rules that President Richard Nixon has to turn over subpoenaed White House tape recordings to the Watergate special prosecutor. 1975: An Apollo spacecraft splashes down in the Pacific, completing a mission that includes the first-ever docking with a Soyuz capsule from the Soviet Union.

An Apollo spacecraft splashes down in the Pacific, completing a mission that includes the first-ever docking with a Soyuz capsule from the Soviet Union. 1998: A gunman bursts into the U.S. Capitol, killing two police officers before being shot and captured. (The shooter, Russell Eugene Weston Jr., is being held in a federal mental facility.)