Evidence from emigration, genealogical, and church (Perpetual Emigrating Fund) records proves the Mansfield family traveled to Utah in 1863. They sailed to America in 1863 on the ship Cynosure and endowed in March 1864, prior to the arrival of that season's emigration. They had to have traveled to Utah in 1863. His given name was spelled "Jarvis" on the ship passenger list and "Jabez" on the 1870 Utah census.
Birth date is confirmed by his death certificate.