April 18

• April 18, 1506
  The cornerstone of new St. Peter's Basilica is laid by order of Pope Julius II after demolition of the ancient basilica
• April 18, 1521
  Martin Luther confronts the emperor Charles V in the Diet of Worms and refuses to retract his views which led to his excommunication
• April 18, 1663
  Osman declares war on Austria beginning Austro-Turkish War
• April 18, 1688
  Jacobite army begins siege of Derry in Ireland
• April 18, 1888
  The Imperial British East Africa Company, the administrator of British East Africa, is incorporated in London, England
• April 18, 1906
  At 5:13 a.m., an earthquake estimated 8.0 on the Richter scale strikes San Francisco, caused by a slip of the San Andreas Fault over a segment about 275 kilometers long, killing estimated 3,000 people from the quake and fires and destroying over 80% of the city
• April 18, 1924
  First crossword puzzle book is published in USA by Simon and Schuster
• April 18, 1949
  Republic of Ireland withdraws from British Commonwealth
• April 18, 1951
  France, West Germany and Benelux form European Steel and Coal Community by Treaty of Paris, making one more step to the founding of the European Union
• April 18, 1974
  Red Brigade, a paramilitary organization, kidnaps Italian Attorney General Mario Sossi
• April 18, 1980
  Zimbabwe, formerly Southern Rhodesia, declares independence from United Kingdom and Robert Mugabe becomes Prime Minister