Which regions were added to the United States during westward expansion?

• A. Great Plains and Rocky Mountains
• B. Appalachian Mountains and Great Lakes
• C. Gulf Coast and Florida Peninsula
• D. Sierra Nevada and Cascade Range

Answer: (A)

Westward expansion involved moving settlement beyond the original United States into the vast interior and toward the Pacific. The interior lands opened up most notably across the Great Plains and the Rocky Mountains. As settlers pushed west, the Plains became important farming and grazing country, while crossing the Rockies marked a major milestone that eventually enabled overland routes and later railroads linking the eastern states with California and Oregon. These two regions symbolize the broad interior expansion that defined the era. The other options describe areas that were already part of the United States earlier or are western ranges, not the main interior regions added during the big westward push.