William J. Glasgow was the son of Edward J. and Harriet Kennerly Glasgow. His father was at that time in the mercantile and banking business in St.Louis, but had led an adventurous life in the southwest during the days before and during the Mexican War. He served under President Van Buren as American consul at Guaymas, later setting himself up as a trader at Mazatlan. He later fought under Colonel Alexander W. Doniphan, and acted toward the close of that war as American commercial agent at Chihuahua. Two of Glasgow's sisters married sons of General William Clark of the Lewis and Clark Expedition.