On April 20, 1999, the Columbine High School massacre took place in Colorado as two students shot and killed 12 classmates and one teacher before taking their own lives.

In 1812, the fourth vice president of the United States, George Clinton, died in Washington at age 72, becoming the first vice president to die while in office.

In 1863, President Abraham Lincoln signed a proclamation admitting West Virginia to the Union, effective in 60 days (on June 20, 1863).

In 1914, the Ludlow Massacre took place when the Colorado National Guard opened fire on a tent colony of striking miners; about 20 (accounts vary) strikers, women and children died.

In 1916, the Chicago Cubs played their first game at Wrigley Field (then known as Weeghman Park); the Cubs defeated the Cincinnati Reds 7-6.

In 1938, “Olympia,” Leni Riefenstahl’s documentary about the 1936 Berlin Olympic games, was first shown in Nazi Germany.

In 1971, the Supreme Court unanimously upheld the use of busing to achieve racial desegregation in schools.

In 1972, Apollo 16′s lunar module, carrying astronauts John W. Young and Charles M. Duke Jr., landed on the moon.

In 1986, following an absence of six decades, Russian-born pianist Vladimir Horowitz performed in the Soviet Union to a packed audience at the Grand Hall of the Tchaikovsky Conservatory in Moscow.

In 1988, gunmen who had hijacked a Kuwait Airways jumbo jet were allowed safe passage out of Algeria under an agreement that freed the remaining 31 hostages and ended a 15-day siege in which two passengers were slain.

In 2003, U.S. Army forces took control of Baghdad from the Marines in a changing of the guard that thinned the military presence in the capital.

In 2010, an explosion on the Deepwater Horizon oil platform, leased by BP, killed 11 workers and caused a blowout that began spewing an estimated 200 million gallons of crude into the Gulf of Mexico. (The well was finally capped nearly three months later.)

Today’s Birthdays: Actor George Takei is 84. Actor Judith O’Dea is 76. Actor Jessica Lange is 72. Actor Veronica Cartwright is 72. Actor Crispin Glover is 57. Actor Andy Serkis is 57. Olympic silver medal figure skater Rosalynn Sumners is 57. Reggae singer Stephen Marley is 49. Rock musician Marty Crandall is 46. Actor Joey Lawrence is 45.