On this day, July 20 ...

1969: Astronauts Neil Armstrong and Edwin "Buzz" Aldrin become the first men to walk on the moon after reaching the surface in their Apollo 11 lunar module.

Also on this day:

This picture, taken at the border at Nogales, Ariz., in 1916, shows, from left, Gen. Alvaro Obregon, Gen. Pancho Villa and Gen. John J. Pershing in a friendly meeting. (AP Photo)

1923: Mexican revolutionary leader Pancho Villa is assassinated by gunmen in Parral.
1944: An attempt by a group of German officials to assassinate Adolf Hitler with a bomb fails as the explosion only wounds the Nazi leader.
1968: The first International Special Olympics Summer Games, organized by Eunice Kennedy Shriver, are held at Soldier Field in Chicago.
1976: America's Viking 1 robot spacecraft makes a successful, first-ever landing on Mars.
1977: A flash flood hits Johnstown, Penn., killing more than 80 people and causing $350 million worth of damage.
1977: The U.N. Security Council votes to admit Vietnam to the world body.
1982: Irish Republican Army bombs explode in London parks, killing eight British soldiers, along with seven horses belonging to the Queen's Household Cavalry.

1990: Supreme Court Justice William J. Brennan, one of the court's most liberal voices, announces he is stepping down.

1993: White House deputy counsel Vincent Foster Jr., 48, is found shot to death in a park near Washington, D.C.; his death is ruled a suicide.

James Holmes, the man who killed 12 people and wounded 58 others when he opened fire at a movie theater in Aurora, Colorado, in 2012, did what he did due to a range of factors "in an unimaginably detailed and complex confluence," a psychiatrist who interviewed Holmes said in a new book. (RJ Sangosti/The Denver Post via AP, Pool, File)

2012: Gunman James Holmes opens fire inside a crowded movie theater in Aurora, Colo., during a midnight showing of "The Dark Knight Rises," killing 12 people and wounding 70 others. (Holmes would be convicted of murder and attempted murder, and sentenced to life in prison without the possibility of parole.)

2019: Marvel's "Avengers: Endgame" passes "Avatar" to become the highest-grossing film of all time.