Containing nearly 57,000 acres of public land, the San Pedro Riparian National Conservation Area (NCA) is between the international border and St. David, Arizona. One of the most important riparian areas in the United States, the San Pedro River’s stretch is home to more than 80 species of mammals, two native species and several introduced species of fish, more than 40 species of amphibians and reptiles, and 100 species of breeding birds. It also provides habitat for 250 species of resident birds. The NCA features the intact remains of the Spanish Presidio Santa Cruz de Terrenate, a Spanish fortress marking the northern extension of New Spain into the New World. The NCA is home to Murray Springs Clovis Site, a significant archaeological resource, containing evidence of the earliest known people to inhabit North America.