This physiographic region covers most of the state and extends
northward into Texas and a short distance southward into Veracruz.
According to Tamayo (1949) and Vivo (1953), the Gulf Coastal Plain is
formed by sedimentary rocks from Mesozoic to Pleistocene in age. The
most common type of soil is Rendzin, especially in the coastal area.
Elevations range from sea level to 300 meters. The area is in general a
flat plain inclined to the sea but this plain is broken by several
small sierras. The more important of these are the Sierra de
Tamaulipas, which rises to more than 1000 meters, and the Sierra San
Carlos, which has a maximum elevation of approximately 1670 meters. The
Sierra de San Jose de las Rucias is smaller.