South of Harlingen, US-83 merges with US-77 for the final 26 miles to Brownsville, where you may well feel like you’ve unknowingly crossed the border into Mexico. One of the most historic cities in Texas, Brownsville retains its Spanish and Mexican heritage more than most places, particularly in the architecture of the downtown district around Elizabeth Street, which runs northwest from the 24-hour border crossing at Matamoros, Mexico. U.S.-Mexico trade supports the local economy via a Union Pacific rail terminus connected with Mexico’s national railway over the Rio Grande; also, a 17-mile deep-sea channel in the river delta links the city with the U.S. Inland Waterway System and the Gulf of Mexico.

Besides the historic downtown, another must-see is Gladys Porter Zoo (956/546-2177, daily, $12 adults) at Ringgold and East 6th Streets, with a good show of unexpected and local creatures hailing from around the world.