Brazos Island is a barrier island

Barrier island

Barrier islands, a coastal landform and a type of barrier system, are relatively narrow strips of sand that parallel the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen...

 on the Gulf Coast

Gulf Coast of the United States

The Gulf Coast of the United States, sometimes referred to as the Gulf South, South Coast, or 3rd Coast, comprises the coasts of American states that are on the Gulf of Mexico, which includes Texas, Louisiana, Mississippi, Alabama, and Florida and are known as the Gulf States...

 of Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, south of the town of South Padre Island

South Padre Island, Texas

South Padre Island is a town in Cameron County, Texas, United States. It is part of the Brownsville–Harlingen Metropolitan Statistical Area. It may be included as part of the Brownsville–Harlingen–Raymondville and the Matamoros–Brownsville metropolitan areas. The population was 2,816 at the...

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History

The island is also known as Brazos Santiago Island, a reference to the port of Brazos Santiago, the first Spanish settlement on the island. Later it became the Port of Matamoros. With a draft of 31 feet, it was perhaps the best naturally occurring seaport in the Western Gulf of Mexico. No one knows who named this excellent seaport, but many think it was Alonso Alvarez de Pineda in 1519. Mystery surrounds the subject, as the existence of a natural seaport in those days would have been an important military secret. Later, in 1846, it was the first military objective of the US Navy, in support of General Zackary Taylor's invasion of Mexico. Control over this important seaport was said by Harvard historian Leroy Graf to be the primary reason for the US aggression against Mexico.

The island is the southernmost barrier island in Texas, separated from the delta landmass of the Rio Grande

Rio Grande

The Rio Grande is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico – United States border. Its length varies as its course changes...

 by unnamed channels. The island's northern end is separated from South Padre Island

South Padre Island

South Padre Island is a barrier island in the U.S. state of Texas. It is located in Cameron County and is a popular vacation destination because the resort city South Padre Island is located on the island. The island itself is considered to have been settled by Padre Jose Nicolas Balli, who had a...

 by the Brazos Santiago Pass. The island is oriented generally north-south, with the Gulf of Mexico

Gulf of Mexico

The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

 on the east, and South Bay

South Bay (Texas)

South Bay is a bay in the Laguna Madre in Texas separated from the Gulf of Mexico by Brazos Island. It is the southernmost bay in Texas, about north of the Texas-Mexico Border....

 on the west. In the course of the natural processes of erosion and sedimentation, the island is not always surrounded by water, but can be connected to the mainland.

During the 1860s Union soldiers occupied the island and it's strategic harbor, during the Civil War and launched the Brazos Santiago expedition from the island which led to the war's last battle known as the Battle of Palmito Ranch

Battle of Palmito Ranch

The Battle of Palmito Ranch, also known as the Battle of Palmito Hill and the Battle of Palmetto Ranch, was fought on May 12–13, 1865, during the American Civil War. It was the last major clash of arms in the war...

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Modern Times

The island is uninhabited. Brazso Santiago Pass on its north end, is the current ship channel for the Port of Brownsville. Brazos Island State Scenic Park, also known as Brazos Island State Recreation Area, is located on the island. The beach at this state park is known as "Boca Chica."