Work on the fort began in 1865 on ground purchased from Christian Sorenson. The fort was 214 feet square, with walls 10 feet high and 2 feet thick, and with bastions 10 feet square at the four corners, with port holes in the walls and bastions. Inside the fort, a one-room rock building erected by Jens Jensen was used for many years as a tithing office and is now the Relic Hall of Old Fort Camp. The enclosure was large enough to shelter all families, and the stone used was taken from the old quarry northeast of Salina.