The United States of America and Canada are the largest countries of North America. This broad land crosses the tropic, the temperate and the frigid zones, which makes its climate complex. It covers an area of about 24,709,000 square kilometers (6,105,661,000 acres). Like other continents, it also has many wonders which can be regarded as the landmarks, including the famous Niagara Falls, the Rocky Mountains, the St. Lawrence Seaway, the Gulf of Mexico, the Great Lakes and Greenland.