David Rice Atchison was a mid-19th century Democratic United States Senator from Missouri. He served as President pro tempore of the United States Senate for six years. Atchison served as a major general in the Missouri State Militia in 1838 during Missouri's Mormon War and as a Confederate brigadier general during the American Civil War under Major General Sterling Price in the Missouri Home Guard. Some of Atchison's associates claimed that for 24 hours—Sunday, March 4, 1849, through noon on Monday—he may have been Acting President of the United States. This belief, however, is dismissed by nearly all scholars.

The 1838 Mormon War, also known as the Missouri Mormon War, was a conflict between Mormons and non-Mormons in Missouri from August to November 1838, the first of the three "Mormon Wars".