Historic Event
May 2 US President Andrew Johnson offers $100,000 reward for capture of Jefferson Davis
Historic Event
May 9 President Andrew Johnson issues a proclamation declaring armed resistance in the South is virtually at an end; this is the commonly accepted end date of the American Civil War
- May 10 Confederate President Jefferson Davis captured by Union troops at Irwinsville Georgia (US Civil War)
- May 10 Major General Sam Jones, the Confederate military leader in Florida, South Carolina and South Georgia, surrenders to Union forces
- May 11 Confederate Brigadier General Meriwether Jeff Thompson surrenders at Jacksonport, Arkansas
- May 12 Last land action of Civil war at Palmito Ranch, Texas
- May 13 Battle of Palmito Ranch, near Brownsville, Texas: final engagement of the American Civil War, Private John Jefferson Williams of B Company, 34th Regiment Indiana Infantry is last man killed
- May 17 The International Telegraph Union (later the International Telecommunication Union) is established
- May 23 -24] Victory parade in Washington, D.C. (Grand Review)
- May 23 Flag flown at full mast over White House for the first time since Lincoln was shot
- May 26 Battle of Galveston Texas, surrender of Edmund Kirby Smith