Humphreys was born in Claiborne County, Mississippi, on the Bayou Pierre. He was educated in New Jersey and enrolled at West Point in the same class as Robert E. Lee. However, he was expelled in 1826 when he participated in a "Christmas frolic" that ended up turning into a riot. Upon his return to Mississippi, he was elected to the state senate representing his native county and served from 1839 to 1844. In 1846, he moved to Sunflower County, Mississippi, founded Itta Bena, and continued as a planter.