For the remainder of the war, Davidson held various administrative commands in Mississippi. He was mustered out of the volunteer service on January 15, 1866. On January 13, 1866, President Andrew Johnson nominated Davidson for appointment to the grade of brevet major general of volunteers to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on March 12, 1866. On April 10, 1866, President Johnson nominated Davidson for appointment to the grade of brevet brigadier general, U.S. Army, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on May 4, 1866. On July 17, 1866, President Johnson nominated Davidson for appointment to the grade of brevet major general, U.S. Army, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on July 23, 1866.