John Seabrook Sydnor, merchant and slave trader, was born in Hanover County, Virginia, on October 20, 1812. He married Sarah Columbia White of Richmond, Virginia, on December 22, 1830, and the couple had five daughters and two sons. Sydnor came to Texas on an inspection tour in 1838, returned to Virginia for his family in 1839, and in January 1840 arrived at Galveston on the Austin with a house that he had had framed in Virginia and shipped in sections. By 1842 he served on the city board of aldermen and operated a profitable commission and real-estate business, J. S. Sydnor & Company. As mayor of Galveston in 1846–47, he promoted establishment of schools, organization of the police and fire departments, and general public improvement. He promoted development of a city market, chamber of commerce, and railroad construction. Sydnor served in the coast guard, built two steamboats in 1843 to haul cotton, and in 1845 built a brick wharf on which he constructed a storage warehouse. In 1847 Sydnor built a twenty-four room personal residence, Powhatan House, which serves as one of the oldest examples of Doric Greek Revival architecture in Texas. Through the 1850s Sydnor was a slave dealer in Galveston, where he held public auctions at his establishment on Strand Street. For a time he was commissioned a colonel in the Confederate Army but resigned to go into the auction and commission business in Houston. He was sent to Richmond to buy cannons for Texas defense. In 1866 Sydnor moved to New York and went into a brokerage business. He died on September 7, 1869, while on a visit at his son's home at Lynchburg, Texas. He is buried in the Oleander Cemetery in Galveston.