1796: English physician Edward Jenner inoculated 8-year-old James Phipps against smallpox by using cowpox matter.
1804: The Lewis and Clark expedition to explore the Louisiana Territory as well as the Pacific Northwest left camp near present-day Hartford, Ill.
1900: The Olympic games opened in Paris as part of the 1900 World's Fair.
1940: The Netherlands surrendered to invading German forces during World War II.
1948: According to the current-era calendar, the independent state of Israel was proclaimed in Tel Aviv.
1955: Representatives from eight Communist bloc countries, including the Soviet Union, signed the Warsaw Pact in Poland.
1961: Freedom Riders were attacked by violent mobs in Anniston and Birmingham, Ala.
1988: 27 people, mostly teens, were killed when their church bus collided with a pickup truck going the wrong direction on a highway near Carrollton, Ky.
1998: The hit sitcom Seinfeld aired its final episode after nine years on NBC.
Associated Press