- Jan 17 A group of Modoc warriors defeats the United States Army in the First Battle of the Stronghold, a part of the Modoc War.
- Feb 20 British Naval Officer John Moresby discovers the site of Port Moresby, Papua New Guinea and claims it for Britain
- May 27 Heinrich Schliemann discovers "Priam's Treasure" a cache of gold and other objects in Hisarlik (Troy) in Anatolia
- Jun 5 Sultan Bargash bin Said under British pressure closes the infamous slave market of Zanzibar in modern day Tanzania
- Sep 18 Government bond agent Jay Cooke & Co collapses, causing panic on Wall St, the start of the panic of 1873 and the Long depression
US Congress enacts the Comstock Law, making it illegal to send any "obscene, lewd, or lascivious" books through the mail
On March 3, 1873