The church measures 150 feet long, 35 feet wide, and 29 feet high. Its long, narrow form reflected the height of the trees available for beams. Its windows were built high for protection and to keep the adobe walls from collapsing under their weight, and specially treated rawhide covered the window openings instead of glass. Military use at Mission San Diego began in 1847, when the Mormon Volunteer Battalion of the U.S. Cavalry lived on the grounds. The soldiers added a second floor inside the church for barracks, used the ground floor as a stable, and reached the windows by exterior ladders that served as doors. The Army of the Pacific lived at Mission San Diego from 1851 to 1858, and the mission remained Army headquarters until 1862, when Abraham Lincoln deeded the mission ruins and 22 surrounding acres back to the Church. In 1931, the building was restored to the specifications and appearance of the church of 1813. Original materials in the building include the wooden beams over the doorways, the adobe bricks in the baptistry arch, and the dark floor tiles made by the padres and the Indians.