I'm open to challenge on this, but the Rocky Mountains, the Sierra Nevada Mountains and the Cascade Mountains are essentially tied for second tallest. I think the Sierra Nevada Mountains may technically be the tallest by a smidgin but what's 65 feet when your talking about 14,500.
For general interest the Alaska Range is the tallest by a wide margin.
The rocky mountains!
Rocky Mountains........... who wouldn't know that
Rock and the Appalachian mountains
Appalachian Mountains.
Mt. Mkinley
the Appalachian mountain range
rocky mountains sierra madres
rocky mountains sierra madres
rocky mountains sierra madres
rocky mountains sierra madres
Appalachian Mountains
Mount Rainier is the most prominent mountain in the contiguous US.The tallest mountain in the continental US (and in the US, period) is Mt. McKinley/Denali in Alaska.('Largest' is ambiguous, since it could be taken to refer to volume rather than height, and that's much harder to judge... where does one mountain leave off and the next in the chain begin?)