North America South America Europe Asia Africa Australia Antarctica Eurasia Atlantic Ocean Pacific Ocean Mississippi River Missouri River Ohio River Columbia River Colorado River Rio Grande Great Lakes Gulf of Mexico This ocean served as a highway for explorers, early settlers and later immigrants Atlantic Ocean This river was considered a gateway to the West. Ohio River In the Midwest Port cities grew here as shipping and trading centers. along the Great Lakes These two rivers were transportation arteries for farm and industrial products. They were links to ports Mississippi River Missouri River This river was explored by Lewis and Clark. They followed it to the Pacific Ocean. Columbia River This river formed the Grand Canyon. It was first explored by the Spanish explorer, Coronado. Colorado River This river forms the border between the United States and Mexico Rio Grande This body of water provided the Spanish and the French with exploration routes into Mexico and other parts of the Americas. Gulf of Mexico