What are the two largest mountain ranges in the u. s. a and where are they located?

The largest is the rocky mountains. This mountain range is 3,000 miles long, starting from British Columbia in Canada and extending south into New Mexico.

The second the Appalachian mountains extend for almost 2,000 miles (3,200 km) from the Canadian province of Newfoundland and Labrador to central Alabama in the United States,