Dec. 17 (UPI) -- On this date in history:
In 1790, the Aztec Calendar, or Solar Stone, was uncovered by workmen repairing Mexico City's Central Plaza.
In 1903, Orville Wright made history's first sustained airplane flight, lasting 12 seconds and covering 120 feet near Kitty Hawk, N.C. His brother Wilbur flew 852 feet later that day.
In 1925, U.S. Army Gen. William "Billy" Mitchell, considered to be the father of the U.S. Air Force, was found guilty of conduct prejudicial to the good of the armed services. He was awarded the Medal of Honor 20 years after his death.
In 1939, the Nazi warship Graf Spee was scuttled off the coast of Uruguay as British vessels pursued it after the Battle of the River Plate. United Press reporter Roscoe Snipes observed the explosions aboard an airplane.
In 1944, the more than 110,000 Japanese Americans who had been relocated from the West Coast shortly after the 1941 Japanese attack on Pearl Harbor were told they would be allowed to return home on Jan. 2.
In 1967, the Clean Air Act is signed into law by President Lyndon B. Johnson.
In 1975, a federal jury in Sacramento sentenced Lynette Alice "Squeaky" Fromme to life in prison for her attempted assassination of U.S. President Gerald R. Ford. She was released from prison in August 2009.
In 1989, The Simpsons, which began as a feature of The Tracy Ullman Show, had its first stand-alone episode broadcast. The popular animated series has spurred look-alike contests, college classes, tattoos and controversy.
In 1997, New Jersey became the first state in the United States to permit same-sex couples to adopt children.
In 2004, the United States officially forgave all of the $4.1 billion owed the government by Iraq and urged other creditors to do the same.
In 2010, Mohamed Bouazizi self-immolated in protest of his treatment at the hands of a municipal official. This would prove to be the catalyst for the Tunisian Revolution and set the stage for the Arab Spring.