In 1867, he was nominated and confirmed for appointment to the grade of brevet brigadier general in the Regular Army, to rank from April 9, 1865.

He entered the United States Military Academy at West Point in July 1852, and graduated four years later standing third out of 49 cadets.

During the Peninsula Campaign that March–July, McAlester was singled out twice for his conduct, winning brevets to major and to lieutenant colonel on July 1, 1862.

[1] That fall McAlester was appointed the lead engineer of the Department of Ohio from October 30, 1862 into January 1863, when he joined the Army of the Tennessee to perform the same duty until August 9.

[1] During the course of his duties in the Civil War, McAlester prepared several detailed maps of Confederate fortifications the Federals encountered.