Complex sentence: Robert Gordon had immigrated to Cotton Gin Port, Mississippi, from Scotland; married Mary Elizabeth Walton; excelled as an Indian trader and landowner; and founded the town of Aberdeen in Monroe County, Mississippi.
Split into simpler sentences: Robert Gordon had immigrated to Cotton Gin Port, Mississippi, from Scotland. He excelled as an trader in the Native American communities and a landowner, and founded the town of Aberdeen in Monroe County, Mississippi.