RUPERT POINT. Rupert Point is a cape (at 28°36' N, 96°24' W) in eastern Calhoun County. It is the tip of a peninsula between Keller Bay to the east and Lavaca Bay to the west and forms the southern point of a narrow strait between the bays; Mud Point, about a half mile across the narrow waterway, forms the northern point of the strait. Rupert Point consists of poorly drained soil, which is occasionally inundated by windblown seawater. In 1985, largely because of these conditions, the point was devoid of settlement and man-made structures.