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 most scholars.