Billy himself doesn't appear in the historical record until 1873 in Santa Fe, but in the 1860s, William Antrim (Billy's future stepfather) and Catherine McCarty (Billy's mother) are known to have lived at various addresses in Indianapolis quite near one another. Billy and his brother were likely just toddlers living with their mother at the time. This is the first documented evidence of the whereabouts of any of the McCarty family in the historical record.