Complex sentence: Following the Civil War, successful tobacco merchant Thomas Henry Mathis sought to expand over-sea trading routes into Texas, so in 1867, he and cousin J.M. Mathis founded a wharf at the site of what would later become the town of Rockport.
Split into simpler sentences: Following the Civil War, successful tobacco merchant Thomas Henry Mathis sought to expand business by establishing additional over-sea trading routes into Texas. To accomplish this goal, in 1867 he and cousin J.M. Mathis built a wharf at the site of what would later become the town of Rockport.