306: Constantine I is proclaimed Roman Emperor by his troops

1814: English engineer George Stephenson introduces his first steam locomotive, a traveling engine designed for hauling coal on the Killingworth wagonway, named Blücher

1943: Benito Mussolini is dismissed as Italian Prime Minister and arrested on the authority of King Victor Emmanuel III

1944: World War II: Operation Spring is one of Canada’s bloodiest days, with 1,444 casualties, including 441 killed in a single day

1997: Scientists announce the first human stem cells to be cultured in a laboratory using tissue taken from aborted human embryos

Source: Onthisday.com