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Events
- 1861 – American Civil War: First Battle of Bull Run – At Manassas Junction, Virginia, the first major battle of the war begins (Confederate victory).
- 1865 – In the market square of Springfield, Missouri, Wild Bill Hickok shoots Dave Tutt dead in what is regarded as the first true western showdown.
- 1873 – At Adair, Iowa, Jesse James and the James–Younger Gang pull off the first successful train robbery in the American Old West.
- 1877 – After rioting by Baltimore and Ohio Railroad workers and the deaths of nine rail workers at the hands of the Maryland militia, workers in Pittsburgh stage a sympathy strike that is met with an assault by the state militia.
- 1919 The dirigible Wingfoot Air Express crashed into the Illinois Trust and Savings Building in Chicago, killing 12 people.
- 1925 – Scopes Trial: In Dayton, Tennessee, high school biology teacher John T. Scopes is found guilty of teaching evolution in class and fined $100.
- 1931 – CBS's New York City station begins broadcasting the first regular seven days a week television schedule in the U.S.
- 1944 – World War II: Battle of Guam – American troops land on Guam starting the battle (ends on August 10).
- 1961 – Mercury program: Mercury-Redstone 4 Mission – Gus Grissom piloting "Liberty Bell 7" becomes the second American to go into space (in a suborbital mission).
- 1969 – Neil A. Armstrong and Edwin "Buzz" Aldrin become the first men to walk on the Moon, during the Apollo 11 mission.
- 1997 – The fully restored USS Constitution (aka "Old Ironsides") celebrates her 200th birthday by setting sail for the first time in 116 years.
- 2002 – Telecom giant WorldCom files for Chapter 11 bankruptcy protection in the largest such filing in United States history.