George and Magnolia Sealy's neo-Renaissance mansion was completed in 1891 and is thought to be the only building in the South designed by Stanford White.

Their luxurious home, Open Gates, became a center of Galveston business and social life. According to family legend, the construction of the landmark mansion was instigated by a statement made by Magnolia after the birth of the couple's fifth child in 1885, "Sir, I'll give you a second son, if you'll build me the finest home in Galveston."

An elaborate carriage house, designed by Galveston architect Nicholas Clayton, was finished the same year the couple's second son was born.