In 1540 Hernando de Soto undertook an extensive exploration of the present United States. In the same year Francisco Vásquez de Coronado led 2,000 Spaniards and Mexican Indians across today's Arizona–Mexico border and traveled as far as central Kansas, close to the exact geographic center of what is now the continental United States. Other Spanish explorers of the United States make up a long list that includes, among others, Lucas Vásquez de Ayllón, Pánfilo de Narváez, Sebastián Vizcaíno, Juan Rodríguez Cabrillo, Gaspar de Portolà, Pedro Menéndez de Avilés, Álvar Núñez Cabeza de Vaca, Tristán de Luna y Arellano, and Juan de Oñate. In all, Spaniards probed half of today's lower 48 states before the first English colonization attempt at Roanoke Island in 1585.