Isaac traveled with his older sister, Matilda Ann Thomas. According to the company roster found in the Journal History, he made the trip working as one of John Van Cott's teamsters. After arrival to Utah, he moved into the household of his father, Daniel S. Thomas, in Salt Lake City. He and his sister, Matilda, are documented in this company. The rest of the family traveled to the Valley in 1849.
His birth date is confirmed by his mother's records found in the Daniel Stillwell Thomas Family History.