How were the tallest mountains in the United States form?

Tallest how? sticking out of the ground? Above sea level? Above the base of the mountain? Some (those along the west coast) are from volcanoes. Mt. Whitney or Mt. Rainier and the now shorty Mt. St. Helens for instance. read more

Of these 200 highest major summits of the United States, 88 are located in Colorado, 49 in Alaska, 22 in California, 14 in Wyoming, eight in New Mexico, five in Utah, four in Nevada, three in Montana, two in Washington, two in Hawai ʻ i, two in Idaho, and one in Arizona. read more

The Rocky Mountains took shape during a period of intense plate tectonic activity that formed much of the rugged landscape of the western United States. Three major mountain-building episodes reshaped the west from about 170 to 40 million years ago (Jurassic to Cenozoic Periods). read more