Fort Brown (originally Fort Texas) was a military post of the United States Army in Cameron County, Texas during the later half of the 19th century and the early part of the 20th century. Established in 1846, it was the first United States Army military outpost of the recently annexed state. Confederate Army troops stationed there saw action during the American Civil War. In the early 20th century, it was garrisoned in relation to military activity over border conflicts with Mexico. Surviving elements of the fort were designated as a National Historic Landmark in 1960.