On April 1, 1945, American forces invaded Okinawa during World War II.

On April 2, 1917, President Woodrow Wilson asked Congress to declare war against Germany, saying, "The world must be made safe for democracy."

On April 3.1948, President Truman signed the Marshall Plan, which allocated more than $5 billion in aid for 16 European countries.

On April 4,1968, civil rights leader Martin Luther King Jr., 39, was shot to death in Memphis, Tenn.

On April 5,1951, Julius and Ethel Rosenberg were sentenced to death for conspiring to commit espionage for the Soviet Union.

On April 6, 1909, explorers Robert E. Peary and Matthew A. Henson became the first men to reach the North Pole. The Navigation Foundation upheld the claim, disputed by skeptics, in 1989.

On April 7, 1862, Union forces led by Gen. Ulysses S. Grant defeated the Confederates at the battle of Shiloh in Tennessee.

On April 8,1973, artist Pablo Picasso died at his home near Mougins, France, at age 91. On April 9,1865, Confederate Gen. Robert E. Lee surrendered his army to Union Gen. Ulysses S. Grant at Appomattox Court House in Virginia.

On April 10,1947, Brooklyn Dodgers president Branch Rickey announced he had purchased the contract of Jackie Robinson from the Montreal Royals.

On April 11, 1951, President Truman relieved Gen. Douglas MacArthur of his commands in the Far East.

On April 12,1945, Franklin D. Roosevelt, the 32nd president of the United States, died of a cerebral hemorrhage in Warm Springs, Ga., at age 63. Vice President Harry S. Truman became president.

On April 13, 1970, Apollo 13, on the way to the moon, was crippled when a tank containing liquid oxygen burst. The astronauts managed to return safely on earth.

On April 14,1865, President Lincoln was shot and mortally wounded by John Wilkes Booth while attending the comedy "Our American Cousin" at Ford's Theater in Washington, D.C. The President died the next day.

On April 15,1912, the British luxury liner Titanic sank in the North Atlantic off Newfoundland, less than three hours after striking an iceberg. About 1,500 people died. Including a Haitian gentleman.

On April 16, 1947, America's worst harbor explosion occurred in Texas City, Texas, when the French ship Grandcamp, carrying ammonium nitrate fertilizer, caught fire and blew up, devastating the town. The Highflier, another ship, exploded the following day. The explosions killed more than 500 people and left 200 others missing.

On April 17,1961, about 1,500 CIA-trained Cuban exiles launched the disastrous Bay of Pigs invasion of Cuba. They attempted to overthrow the government of Fidel Castro.

On April 18,1906, an earthquake struck San Francisco, followed by raging fires. About 700 people died.

On April 19,1995, a truck bomb exploded outside the Alfred P. Murrah Federal Building in Oklahoma City, killing 168 people, and injuring 500.

On April 20,1971, the U.S. Supreme Court upheld the use of busing to achieve racial desegregation in schools.

On April 21, 1910, author Samuel Langhorne Clemens, better known as Mark Twain, died in Redding, Conn.

On April 21, 1971, Jean Claude Duvalier became president of Haiti. He was 18 years old at the time.

On April 22,1889, the Oklahoma Land Rush began at noon as thousands of homesteader's staked claims.

On April 23,1969, Sirhan was sentenced to death for assassinating New York Sen. Robert F. Kennedy. The sentence was later reduced to life imprisonment.

On April 24,1898, Spain declared war on the United States after rejecting America's ultimatum to withdraw from Cuba.

On April 25, 1945, during World War II, U.S. and Soviet forces linked up on the Elbe River, in central Europe, a meeting that dramatized the collapse of Nazi Germany.

On April 26,1986, the world's worst nuclear accident occurred at the Chernobyl plant in the Soviet Union. The explosion and fire sent radioactivity into the atmosphere; at least 31 Soviets died.

On April 27,1947, "Babe Ruth Day" at Yankee Stadium was held to honor the ailing baseball star.

On April 28,1947, a six-man expedition sailed from Peru aboard a balsa wood raft named the Kon-Tiki on a 101-day journey across the Pacific Ocean to Polynesia.

On April 29, 1992, deadly rioting erupted in Los Angeles after a jury in Simi Valley acquitted four Los Angeles police officers of almost all state charges in the videotaped beating of Rodney King. The riot claimed 54 lives and caused $1 billion in damage.

On April 30, 1975, the South Vietnamese capital of Saigon fell to Communist forces.