Pass Cavallo, alternately known as Cavallo Pass, is one of five natural water inlets which separate the Gulf of Mexico and Matagorda Bay, in the U.S. state of Texas.René-Robert Cavelier, Sieur de La Salle came ashore in Texas at this point.Matagorda Island Lighthouse was originally built on this site. During the Civil War, Pass Cavallo was a major port of entry and was captured by the UnionCoordinates: 28°23′N 96°24′W / 28.383°N 96.400°W