In the 1850s, Marmaduke Hobby's mother, a widow, moved with her sons to Madison, Florida, and then to Galveston, Texas. Hobby entered a mercantile partnership and established a general store at the new town of St. Mary's of Aransas, Refugio County, about 1857. Although only about twenty-two, he almost immediately became a political leader of the county. Upon the resignation of Henry Lawrence Kinney in 1861, Hobby was elected to the Texas House of Representatives for the Eighth Texas Legislature. Hobby had no children; his wife had children from an earlier marriage.