According to Robert Roberts’ “DR. THOMAS: HIS LIFE & WORK”, John Thomas and his family arrived in Cincinnati in September 1832. They went to the house of a director of a local bank, a man called Brown, with letters of introduction from the latter’s brother, one Col. Brown of London. In a house opposite was a Major Daniel Gano, who was interested in the arrival of a Baptist Minister and his family from England. (The elder John Thomas became a Baptist minister in 1831.) Daniel invited the son and father to dinner, and later turned the conversation to religion. He raised the subject of baptism, and gave John Thomas pamphlets written by Alexander Campbell and Walter Scott. This same Walter Scott preached at a funeral the next Sunday, met Dr. Thomas, and after some intense discussions baptized him in the local canal by moonlight. As Dr. Thomas wrote at the time “in the presence of a few friends I was baptized in the Miami Canal, on Sunday evening, Oct. 14, at 19 1/2 o’clock.” The impression Roberts gives, and most have followed that assumption, is that Dr. Thomas (and I here deliberately use his medical doctor descriptor) did not pursue work as a doctor in Cincinnati.
However, an interesting document recently was given to me (which I have transferred to the safekeeping of the Christadelphian Office in England). It shows that almost immediately upon his arrival in Cincinnati, he applied for membership in the local medical society— a requirement to practice medicine. Thus he became one of about 50 doctors in town — with a population in 1832 of roughly 25,000 — or one in 500, about twice the current US ratio. A little hard to read (after all, it is almost 180 years old), it reads as follows:
First District Medical So. Of Ohio
THIS CERTIFIES, That Doctor John Thomas is a regular member of the First District Medical Society of Ohio, and entitled to all the privileges and benefits secured to legal Medical Practitioners, by the Legislature of the State of Ohio. Cincinnati, Ohio — September 12th, 1832. Wm. Mulford, M.D. Sec’ry.
This document is the oldest original record, of which I have knowledge, of John Thomas in America — and although secular in nature, throws light on his intensions in Cincinnati.
A quick look on the internet revealed that indeed one William Mulford was secretary in the society in that year — at least he signed another certificate for Hiram Cox, which certification was required to practice as a doctor.
So we know that John Thomas intended to practice medicine in Cincinnati, but that intent was altered, at least in part, by meeting Daniel Gano. Perhaps through the providence of God, he instead studied the Christian Gospel for the next several months. He removed to Philadelphia in the spring of 1833, to a city where

he managed to combine a medical practice with preaching his new found gospel. But that, as they say, is another story.