On September 1, 1513, Vasco Núñez de Balboa led an expedition of 190 Spaniards and hundreds of indigenous guides across the Isthmus of Panama. On September 25, 1513, from atop Mount Urrucallala, Balboa became the first European to sight the Pacific Ocean from the Americas. Four days later, on September 29, he reached the shores of the Gulf of San Miguel, claiming the ocean and all its shores for Spain. This expedition marked the beginning of Spanish exploration of the Pacific and accelerated the colonization of the Americas.