1865 - The American Dental Association proposed its first code of ethics.
1866 - The metric system was legalized by the U.S. Congress for the standardization of weights and measures throughout the United States.
1868 - The Fourteenth Amendment to the U.S. Constitution was declared in effect. The amendment guaranteed due process of law.
1896 - The city of Miami, FL, was incorporated.
1914 - World War I officially began when Austria-Hungary declared war on Serbia.
1941 - Plans for the Pentagon were approved by the U.S. House of Representatives.
1942 - L.A. Thatcher received a patent for a coin-operated mailbox. The device stamped envelopes when money was inserted.
1945 - A U.S. Army bomber crashed into the 79th floor of New York City's Empire State Building. 14 people were killed and 26 were injured.
1951 - The Walt Disney film "Alice in Wonderland" was released.
1982 - San Francisco, CA, became the first city in the U.S. to ban handguns.
1991 - Dennis Martinez (Montreal Expos) pitched the 13th perfect game in major league baseball history.
1994 - Kenny Rogers (Texas Rangers) pitched the 14th perfect game in major league baseball history.
1998 - Bell Atlantic and GTE announced $52 billion deal that created the second-largest phone company.
1998 - Monica Lewinsky received blanket immunity from prosecution to testify before a grand jury about her relationship with U.S. President Clinton.
2000 - Kathie Lee Gifford made her final appearance as co-host of the ABC talk show "Live with Regis and Kathie Lee."
2006 - Researchers announced that two ancient reptiles had been found off Australia. The Umoonasaurus and Opallionectes were the first of their kind to be found in the period soon after the Jurassic era.