"Vicksburg". Civil War Trust. Retrieved August 21, 2016.
history.com
Vicksburg Campaign; History.com online website; text: "...The Siege of Vicksburg (May 18, 1863 – July 4, 1863) was a decisive Union victory during the American Civil War (1861–65) ..."; accessed June 2020
National Park Service. Grant's army arrived at the outskirts of Vicksburg on May 19, but formal siege operations began with Grant's Special Order No. 140 on May 25 (Simon, p. 267).