October 20: Shemini Atzeret begins at sunset (Judaism, 2008); Birth of the Báb, a holy day in the Bahá'í Faith
1708 – Having burned down in the 1666 Great Fire of London, the rebuilt St Paul's Cathedral (pictured) was completed on the 76th birthday of its architect, Christopher Wren.
1818 – The United Kingdom and the United States signed the Treaty of 1818, which settled the Canada – United States border on the 49th parallel for most of its length.
1827 – An allied British, French, and Russian naval force destroyed a combined Turkish and Egyptian fleet at the Battle of Navarino, a decisive moment in the Greek War of Independence.
1967 – Roger Patterson and Robert Gimlin filmed an unidentified subject at Six Rivers National Forest in California who they claimed was a bigfoot.
1973 – Queen Elizabeth II, in her capacity as Queen of Australia, formally opened the Sydney Opera House on Bennelong Point in Sydney Harbour.
