Back when Texas was still Tejas , EL PASO , the second oldest settlement in the United States, was the main crossing on the Rio Grande. It still plays that role today, its 700,000 residents joining with another 1.7 million across the river in CIUDAD JUAREZ , Mexico, to form the largest binational (and bilingual) megalopolis in North America. At first sight, massive railyards fill up much of downtown, the belching smelters of copper mills line the riverfront, and the northern reaches are taken up by the giant Fort Bliss military base, where two museums trace the military history of the city from adobe Spanish outpost to largest air defense center in the western world. Its dramatic setting, however, where the Franklin Mountains meet the Chihuahua desert, gives it a certain bold, rough pioneer edge, bearing more relation to old rather than new Mexico, with little of the pastel softness of the Southwest US. Local legend has it that when Wyatt Earp arrived in sharp-shooting El Paso, he thought it too wild for him, and boarded the first train to Tombstone.