Spain, Portugal, and other European kingdoms sent expeditions and established colonies throughout the New World, converted the native inhabitants to Christianity, and built large trade networks across the Atlantic, which introduced new plants, animals, and food crops to both continents. The search for a westward route to Asia continued in 1513 when Vasco Nuñez de Balboa crossed the narrow Isthmus of Panama to become the first European to sight the Pacific Ocean. The search was completed in 1521, when the Castilian (Spanish) Magellan expedition sailed across the Pacific and reached Southeast Asia.