- 1457 BC Battle of Megiddo: Egyptian forces of Thutmose III defeat a large Canaanite coalition under King of Kadesh. First battle recorded with a reliable account.
- 1705 Queen Anne of England knights Isaac Newton at Trinity College, Cambridge
- 1746 Jacobite Rising 1745: Battle of Culloden, the last battle on British soil: Royalist troops under the Duke of Cumberland defeat the Jacobite army.
- 1900 US Post Office issues 1st books of postage stamps
- 1917 [OS Apr 4] Lenin issues his radical "April Theses" calling for Soviets to take power during Russian Revolution
- 1948 Organization for European Economic Cooperation (EEC) forms in Paris
- 2003 The Treaty of Accession is signed in Athens admitting 10 new member states to the European Union.
Swiss scientist Dr. Albert Hofmann discovers the psychedelic effects of LSD.
On April 16, 1943