North America physical map showing the following elevations, sea level to 649 feet, 650 to 1649 feet, 1650 to 3249 feet, 3250 to 6549 feet, and 6500 feet and higher. The east coast and much of the South, up through the lower Mississippi River valley, is sea level to 649 feet. The upper Mississippi River and Ohio River valleys are 650 to 1649 feet. The Appalachian Mountains are 650 to 3249 feet. Moving west from the Mississippi, elevation steadily rises to the Rocky Mountains, from 3250 to 6500 feet. The elevation remains largely at 1650 feet and higher west of the Rockies, with a sharp drop at the Pacific Ocean. © 2012 The Exploration Company Lewis and Clark traveled from St. Louis, which is beside the Mississippi River. Which of the following correctly describes the land they saw as they traveled to the Pacific Northwest? Flat and low around the Mississippi River, with a sharp and sudden rise to the Rocky Mountains, tapering off slowly to the ocean Flat and low around the Mississippi River, gradually rising to the Rocky Mountains, then tapering off quickly to the ocean Flat but high around the Mississippi River, with a sharp and sudden rise to the Rocky Mountains, dropping off suddenly to the ocean Flat but high around the Mississippi River, quickly rising to the Rocky Mountains, then tapering off slowly to the ocean