What mountain range covers most of the middle of the US?

There are 2 major mountain ranges in the US, both running approximately north-south:

* The Appalachians in the east are old mountains, worn down over time, and stretch from Alabama and Georgia in the south through Maine into Canada as far as Nova Scotia. * The Rockies in the west are much higher, broader mountains. The range runs from the southwestern US well into Canada, in part forming the boundary between British Columbia and Alberta.