- Aug 1 Rotherhithe Tunnel under the Thames opens
- Aug 1 Lombard Street Riot erupts in Philadelphia [1] [2]
- Aug 9 US-Canada border defined by Webster-Ashburton Treaty
- Aug 14 Second Seminole War declared over by US Army Colonel Worth, after nearly 7 years; more than 3000 Seminole Nation survivors re-located from Florida to Oklahoma, only about 300 allowed to remain [1]
- Aug 21 The city of Hobart, Tasmania, is founded.
- Aug 29 Great Britain and China sign Treaty of Nanking, ending the Opium war
- Aug 31 Micah Rugg patents a nuts & bolts machine
- Aug 31 US Naval Observatory authorized by an act of Congress