Today:
1606 – The Union Flag (later known as the Union Jack) was adopted as the flag of England and Scotland.
1861 – The American Civil War began with Confederate forces firing on Fort Sumter in South Carolina.
1877 – The United Kingdom annexed the Transvaal in South Africa.
1934 – The strongest surface wind gust ever recorded on Earth at the time, 231 mph, was measured on Mount Washington, New Hampshire.
1945 – U.S. President Franklin D. Roosevelt died of a cerebral hemorrhage in Warm Springs, Georgia; Harry S. Truman became president.
1955 – The polio vaccine developed by Jonas Salk was declared safe and effective.
1961 – Soviet cosmonaut Yuri Gagarin became the first human to travel into space aboard Vostok 1.
1981 – The first launch of a Space Shuttle, Columbia (STS-1), took place from Kennedy Space Center in Florida.
1992 – Euro Disney Resort officially opened in Marne-la-Vallée, France.
2015 – Hillary Clinton officially announced her candidacy for the Democratic nomination for U.S. President in the 2016 election.