Seymour Brunson was born in the state of New York (some sources say Vermont) in 1798. He served in the War of 1812 and married Harriet Gould in 1823. He joined the Church of Christ (as The Church of Jesus Christ of Latter-day Saints was originally called) in early 1831 while living in Ohio. Soon thereafter, he served a proselyting mission in Ohio, Virginia and Kentucky.
Along with most church members at the time, he subsequently moved to Missouri where he experienced severe persecution and significant financial loss estimated at more than $3,000. He formally appealed for redress but was never compensated for any of his losses.
Brunson served in militias in both Missouri and Illinois. After moving from Missouri on to Nauvoo, Illinois, he became a lieutenant colonel in the Nauvoo Legion. He was also a bodyguard for the Prophet Joseph. People referred to him as Col. Brunson.
Brunson is mentioned in two different sections of the Doctrine and Covenants, section 75 and section 124. At the time of his death in August 1840, the Prophet Joseph spoke at Brunson's funeral. The Prophet noted that up to the moment that he passed on, Brunson testified of the truthfulness of the gospel he had embraced in life. Of particular note, it was during that discourse that the Prophet Joseph publicly introduced the doctrine of baptism for the dead.