As of 2005, approximately 450,000 people live in Matamoros and its immediate surroundings. Growth is rapid, averaging 15% annually, accelerated by migratory immigration into South Texas. 1990 US census counted 9,581 in the City of Brownsville, Texas, sister city to Matamoros and directly across the International Bridge.

Tamaulipas ("high mountains"), borders southernmost Texas and possesses long stretches of beaches and lagoons. In the west, arid mountains and tropical valleys of Sierra Madre Oriental, to its north are arid plains. Northern population still reflects migration from the interior, southern portion still consists mainly of Huastec Indians, descendants of a Mayan tribe.

Brownsville sits at the mouth of the Rio Grande River, where it finally joins the Gulf of Mexico. On flat terrain, the climate is very hot and very humid year long. The region experiences heavy rains at times, and is affected by the gulf streams and the hurricane season in South Texas.

Once crossed over the International Bridge into Brownsville, Texas, the following distances are in effect: 150 miles East to deep water port of Corpus Christi, Texas; 290 miles North to San Antonio, Texas on I-35; 517 miles North to Dallas, Texas; and 715 miles to El Paso, Texas.