The transition level in the US is 180.
The highest point in the contiguous US is not in the Rockies, but rather, in California's Sierra Nevadas. It is Mt. Whitney which stands 14,505 ft. The highest point in the US overall is Mt. McKinley (Denali) in Alaska which reaches 20,320 ft (so much for THAT theory!
). There are 10 peaks in Alaska which are taller than Mt. Whitney, and six of them are above 16k.
The highest point in the US Rockies comes in at number 14 in the US peak list, at 14,400 ft.
Dave