October 20
1740. Maria Theresa takes the throne of Austria, setting off the war of Austrian succession as Prussia and France, on the pretext that Salic Law forbade her from ascending to the Hapsburg throne. The war will drag in all of Europe, and also be known as King George's War in the colonies.
1803. The US Senate ratifies the Louisiana Purchase, by a vote of 24-7. I cannot confirm that the 7 nay votes were cast by drunken morons, but it does seem likely.
1818. The Convention of 1818 settles the border between the US and Canada at the 49th parallel for much of the length of the border.
1947. The House Un-American Activities Committee begins its investigation of Hollywood, which will eventually result in the blacklisting of some 300 individuals, barring them from work for years. After the fall of the Committee's spiritual leader of sorts in the Senate, Joseph McCarthy, it will lose favor. By 1959 former President Truman will refer to the committee as "the most Un-American thing in the country today."
1967. Patterson and Gimlin film their purported bigfoot.
1973. The Saturday Night Massacre -- President Nixon fires US Attorney General Elliot Richardson, and Deputy Attorney General William Rickelshaus after they refuse to fire special prosecutor Archibald Cox, who is doing far too good a job of digging into the Watergate situation. Next in line, who is willing to do the dirty deed, is Solicitor General Robert Bork. Bork remains with the DOJ post-firing, not leaving until the change in administrations in 1977. His Supreme Court nomination fight in 1987 would lead to high drama, and his eventual rejection by the Senate.
1977. A plane carrying Lynyrd Skynyrd crashes in Mississippi, killing the lead singer, guitarist, a backup singer, and road manager, as well as the pilot and copilot.