The Rio Grande, flowing through 1500-foot canyons, makes a ninety-degree bend south of Marathon to form the southern border of Big Bend National Park – thanks to its isolation one of the least visited of the US national parks.
A breathtaking 800,000-acre expanse of forested mountains and ocotilla-dotted desert, Big Bend has been home to ranchers, miners, and smugglers, a last frontier for the true-grit pioneers of the American West. Much of the park remains barely charted territory and ruins of primitive Mexican and white settlements are testament to Big Bend's power. Wild animals have fared somewhat better: mountain lions, black bears, roadrunners, and javelinas all roam free. Violent contrasts in topography and temperature result in dramatic juxtapositions of desert and mountain plant and animal life. Despite the dryness, tangles of pretty wild flowers and blossoming cacti erupt into colour each March and April.
Unless you're prepared to do some strenuous hiking, there are few opportunities to see the river itself; the main road is obliged to run across the desert. West of the headquarters at Panther Junction a spur road leads south for about six miles, up into the Chisos Basin, ringed by dramatic peaks. The one gap in the rocky wall here is the Window, looking out over the Chihuahuan Desert. A twelve-mile loop hike to the South Rim is one of the most popular in the park, and the views are humbling.