April 18, 1506: The cornerstone of the current St. Peter's Basilica is laid in the Vatican.
April 19, 1775: American Revolution begins in Lexington, Massachusetts. The "Shot Heard Round the World" took place in Concord later that day.
April 20, 1936: Jews repel an Arab attack in Petach Tikvah Palestine.
April 21, 1789: John Adams sworn in as 1st US Vice President (9 days before Washington).
April 22, 1876: 1st official National League baseball game is played; Boston Red Stockings beat Philadelphia Athletics, 6-5 at the Jefferson Street Grounds, Philadelphia.
April 23, 1348: The Order of Garter founded by English King Edward III, Britain's highest civic or military honor.
April 24, 1898: Spanish–American War: Spain declares war after rejecting US ultimatum to withdraw from Cuba.