The Rocky Mountains are a western region of the United States of America, and offer skiing and snowboarding in the winter, and road and mountain biking, hiking, camping, kayaking, horse-back riding, and white water rafting in the summer.
The largest and most popular entry point into the region is Denver, which is one of North America's principal rail and flight hubs. Domestic flights to the other major cities in the region, like Cheyenne, Boise, Billings, or Jackson, should be easy to find from any American hub airport.
Route 25 is the major north-south highway, leading up from New Mexico, while I-70, I-80, and I-90/94 are the major east-west highways. Be aware that passes do get closed due to inclement weather (snow) in winter months, in particular I-70 is prone to this. Bus routes exist, mostly through Greyhound, but given the long distances, flying is often cheaper than paying for gas and bus fares on the road.
Getting around the Rocky Mountains can be tough. Mountain passes freeze in the winter, as you might expect, and many roads are risky, if not impassable under heavy snow. Moreover, you'll run through more gas per mile in the high altitudes. Flying is often a very good alternative in the winter, since Denver offers flights straight to ski slopes off in the mountains, as well as to virtually all the cities in the region.
During the warmer months, however, driving becomes a great way to explore the region. Some of the most spectacular drives in the country are located here among the high mountains and endless wilderness. It can also be the only way to get to destinations off the beaten path, since, as you might expect, there's not a lot of public transportation in this vast and lightly populated section of the country.