In 1844 medical doctor John Thomas came to America from England. He joined the Disciples of Christ, but decided that its teachings made it the apostate church predicted by the Scripture, and that it was ignoring some important biblical doctrines. He left the Disciples and spent some time organizing societies preaching the need to return to primitive Christianity. In 1849 he wrote Elpis Israel, which started the first stirrings of the Christadelphian faith. The movement crystallised when the War Between the States broke out (1861). The members' doctrine of nonresistance forced them to take a name in order to register as conscientious objectors. The name 'Christadelphian' was first registered by Brother Sam Coffman and six others at the County Courthouse in Ogle, Illinois, and the name spread quickly.

The name 'Christadelphian' come from the Greek words 'Christos' (Christ) and 'adelphoi' (brothers and sisters). The church is also known as the Brethren in Christ.

Christadelphians are both Unitarian and Adventist. They have ecclesias all over the world.

Primary sources: (Very Good)
Handbook of Denominations in the United States by Frank S. Mead, Revised Samuel S. Hill. (Not to be completely trusted).