Portal:United States/Anniversaries/August/August 20
- 1707 – The first Siege of Pensacola comes to an end with the failure of the British to capture Pensacola, Florida.
- 1794 – Northwest Indian War: United States troops force a confederacy of Shawnee, Mingo, Delaware, Wyandot, Miami, Ottawa, Chippewa, and Potawatomi warriors into a disorganized retreat at the Battle of Fallen Timbers.
- 1910 – Extreme fire weather in the Inland Northwest of the United States causes many small wildfires to coalesce into the Great Fire of 1910, burning approximately 3 million acres (12,000 km2) and killing 87 people.
- 1938 – Lou Gehrig hits his 23rd career grand slam, a record that stood for 75 years until it was broken by Alex Rodriguez.
- 1977 – Voyager program: NASA launches the Voyager 2 spacecraft.
- 1986 – In Edmond, Oklahoma, U.S. Postal employee Patrick Sherrill guns down 14 of his co-workers and then commits suicide.