It appears that Joseph Southwick joined the Church of Jesus Christ of Latter-day Saints in 1843 in West Bromwich, England when he was about 34 years old. His first wife probably joined the Church too. When she died, he married Mary Walters, who probably joined the Church near the time of their marriage when she was about 27 years old. He and his family sailed for America in 1849 on the ship Ashland. When they arrived at St. Louis, Missouri, Joseph became ill with cholera and died suddenly. He was buried on a nearby island. His widow and small son Joseph, Jr. eventually made it to Utah, arriving about 1852.
PAF documentation notes and sources:
Joseph Southwick was baptized around 1843 - 1844 in England. We know he was ordained a Priest on February 9, 1844. He and his family emigrated to America in 1849.