Thomas and his wife, Anne, arrived in New York on 23 June 1864 via the ship The General McClellan. They were traveling with Anne's four children by her first marriage. The ship passenger list lists Ann and her children under the married name of Griffiths, but the overland company roster lists them all with Thomas' surname of Williams.
The British Mission Record (as documented in Mormon Migration) indicates that he was an engineer and was 55 years old at the time of the reservation. Just below his name is Ann, still listed a widow, and her children (Elinor, Mary, Ann, and Hannah). Thomas and Ann must have married some time between the time that coordinated their plans with the British Mission and actually made the overland journey.
This family should not be confused with another Thomas and Ann Williams and their children who made trip on both the same ship and overland company. Both Thomas Williams have PEF accounts in ledger C, page 748, with the same entry dates. The account for this Thomas Williams is the one with the balance of 123.05. (Bond number 4376.)