October 27

312 – Constantine is said to have received his famous Vision of the Cross. 1275 – Traditional founding of the city of Amsterdam. 1524 – French troops lay siege to Pavia. 1553 – Condemned as a heretic, Michael Servetus is burned at the stake just outside Geneva. 1644 – Second Battle of Newbury in the English Civil War. 1682 – Philadelphia is founded in the Commonwealth of Pennsylvania. 1775 – King George III expands on his Proclamation of Rebellion in the Thirteen Colonies in his speech from the throne at the opening of Parliament. 1795 – The United States and Spain sign the Treaty of Madrid, which establishes the boundaries between Spanish colonies and the U.S. 1806 – The French Army under Napoleon enters Berlin following the Prussian defeat at the Battle of Jena–Auerstedt. 1810 – United States annexes the former Spanish colony of West Florida. 1838 – Missouri governor Lilburn Boggs issues the Extermination Order, which orders all Mormons to leave the state or be killed. 1870 – Franco-Prussian War: Marshal Bazaine surrenders to Prussian forces at the conclusion of the Siege of Metz along with 140,000 French soldiers. 1904 – The first underground New York City Subway line opens, later designated as the IRT Broadway–Seventh Avenue Line. 1907 – Fifteen people are killed in Hungary when gendarmes opened fire on a crowd gathered at a church consecration. 1914 – World War I: The new British battleship HMS Audacious is sunk by a minefield laid by the armed German merchant-cruiser Berlin. 1916 – Negus Mikael, marching on the Ethiopian capital in support of his son Emperor Iyasu V, is defeated by Fitawrari abte Giyorgis, securing the throne for Empress Zewditu I. 1919 – The Fourth Regional Congress of Peasants, Workers and Insurgents is held by the Makhnovshchina at Oleksandrivsk. 1922 – A referendum in Rhodesia rejects the country's annexation to the South African Union. 1924 – The Uzbek SSR is founded in the Soviet Union. 1930 – Ratifications exchanged in London for the first London Naval Treaty go into effect immediately, further limiting the expensive naval arms race among its five signatories.