The Rio Grande Valley also known by Texans as “The Valley” extends from the mouth of the Rio Grande up the river for a distance of nearly 100 miles. The Spanish first occupied the area around 1750, they settled on the right bank of the river and divided the area north of the river into great cattle-ranch grants. The first American settlement in the area was Brownsville, which was founded as a result of the invasion of Zachary Taylor and the United States Army in the Mexican-American War in 1846. The town, which sprang up around Fort Brown, remained practically the only settlement of a size or distinction in the Valley for over half a century. Due to this, on February 12, 1848, the Texas legislature decreed the existence of Cameron County, and with the signing of the Treaty of Guadalupe-Hidalgo on July 4, the area officially became part of the United States. In December of the same year, Charles Stillman established Brownsville just west of Fort Brown and by election Brownsville was chosen as the County seat.

      Cameron and its surrounding counties (Hidalgo, Willacy, Starr) are the highest in the United States in the size of its Hispanic population, according to the 1990 census. The actual percentage is probably higher than the census figure, since the census often misses migrant farm-workers, undocumented workers and refugees calling The Valley home.