San Andres is the largest of the islands that form the archipelago of San Andres Providence and Catalina. It is 13km (8miles) long and 5km across at its widest, with a total area of 28 square km (11 sq. miles). It is a small, north to south longitudinal mountainous island, covered by coconut palms groves, with an elevation at its high point of 55 m (180 ft). By its geologic and biological origin, the island of San Andrés is rocky, lacking fresh water, streams and without significant vegetation. The local people, who are predominately descended African slaves, are commonly called "raizales."