- Aug 1 Brazil recognizes the Confederate States of America
- Aug 2 Skirmish at Dug Springs, Missouri results in Union victory
- Aug 3 Federal fleet bombards Galveston, Texas
- Aug 5 Enlistment in US Union army increases from 3 months to 2 years
- Aug 5 Naval Engagement at Fernandina, Florida, the USS Vincennes ends rebel blockade
- Aug 5 President Lincoln signs the first US personal Income Tax into law (3% of incomes over $800)
- Aug 5 US Army abolishes flogging
- Aug 6 Lexington, Kentucky - Union military camp forms in neutral state
- Aug 6 The British annex Lagos, Nigeria
- Aug 6 US Congress passes First Confiscation Act
- Aug 10 Battle of Wilson's Creek [Battle of Oak Hills], fought near Springfield, Missouri, General Lyon killed, Confederate victory (US Civil War)
- Aug 12 Skirmish at Texas - rebels are attacked by Apache Indians
- Aug 14 79th NY troops mutinies
- Aug 14 Martial Law is declared at St Louis, Missouri, due to pro-secession sentiment which surged throughout Missouri after the Battle of Wilson's Creek
Lincoln Sends Reinforcements
Aug 15 Abraham Lincoln orders Union reinforcements be sent to Missouri
- Aug 16 Skirmishes at Fredericktown/Kirkville, Missouri
- Aug 16 US President Abraham Lincoln prohibits Union states from trading with Confederacy
- Aug 19 Confederacy Congress allies with government of Missouri
- Aug 20 Skirmish at Jonesboro, MO
- Aug 27 Battle of Cape Hatteras SC-Union troops take Ft Clark
- Aug 28 American Civil War: Battle of Fort Hatteras, North Carolina, 1st combined operation of Union Army and Navy results in Union domination of strategically important North Carolina Sounds
- Aug 29 American Civil War: US Navy squadron captures forts at Hatteras Inlet, North Carolina.
- Aug 30 John Frémont issues proclamation freeing slaves of Missouri rebels
Admirals
Aviators
Gangsters
Generals
Industrialists
Suffragists