James with two of his sons, Jesse and Alexander, volunteered to serve as part of the Mormon Battalion. One of his wives, Mary McRee, and her son George David, also traveled with the Mormon Battalion. His other three wives and children stayed at Council Bluffs until they could be brought to the Salt Lake Valley. Mary’s job was to do the laundry for 16 men. James was the Captain of Company C, and his two sons served in his company as privates. At Santa Fe, James was one of a few placed in charge of a sick detachment which was sent to Pueblo, Colorado to spend the winter. Mary accompanied him and cared for the sick men. The next spring, the company traveled by way of Fort Laramie and arrived in the Salt Lake Valley five days after the Brigham Young Pioneer Company.
In August, after arriving to Salt Lake City, James went to California with his son Jesse, Abner Blackburn, and Lysander Woodworth. Samuel Lew later joined their group. They returned to Salt Lake City on November 16, 1847.