On April 22, 1889, the Oklahoma Land Rush began at noon as thousands of homesteaders staked claims to nearly 1.9 million acres of land that was formerly part of Indian Territory. By the end of the day, the cities of Oklahoma City and Guthrie were established with as many as 10,000 settlers each.

In 1915, German forces unleashed their first full-scale use of chlorine gas at the Second Battle of Ypres in Belgium during World War I. Thousands of Allied soldiers are believed to have died from the attacks.

In 1970, an estimated 20 million Americans participated in gatherings for the first Earth Day, a series of events proposed by Sen. Gaylord Nelson of Wisconsin to promote environmental protections.

In 1994, Richard M. Nixon, the 37th president of the United States and the first to resign from office, died at a New York hospital four days after having a stroke. He was 81.