New England's Dark Day: A combination of thick smoke and heavy cloud cover causes complete darkness to fall on Eastern Canada and the New England area of the United States at 10:30 A.M.

Apollo 10 is launched

Mount St. Helens erupts in Washington, United States, killing 57 people and causing $3 billion in damage.

Battle of Monte Cassino – Conclusion after seven days of the fourth battle as German paratroopers ("Fallschirmjäger") evacuate Monte Cassino.

In Laurel, Maryland, Arthur Bremer shoots and paralyzes Alabama Governor George Wallace while he is campaigning to be become President.

Anniversary of the first public performance of John Philip Sousa’s march “The Stars and Stripes Forever,” at Philadelphia, PA.

Skylab, the United States' first space station, is launched.

Edward Jenner administers the first smallpox vaccination.

The Lewis and Clark Expedition departs from Camp Dubois and begins its historic journey by traveling up the Missouri River.

Jamestown, Virginia is settled as an English colony.