Under the same ownership as Breckenridge and acquired in 1997 by Vail Resorts Inc., Keystone's numerous claims to fame include the largest night-skiing operation in Colorado and North America's biggest ice rink (five acres).

The resort's ski area is relatively unusual, resembling Les Deux Alpes in France, in that the trails and mountains stack out in a line behind the resort itself, rather than following the more common model of running side-by-side above the resort valley. The mountains become slightly higher and slightly steeper the further back you go, creating Keystone's heavily promoted 'Outback' area beneath Outback Peak, the third and furthest mountain from the resort base. Here you will find the above treeline open bowl skiing that has become a requirement of all major Western US ski areas, as well as the equally obligatory tree skiing. In common with most of the resorts in the area Keystone's history is relatively short with the familiar meteoric rise to fame of neighbours such as Copper Mountain and Vail.

Keystone opened in 1970 with three lifts and a $5 lift ticket attracting 75,000 visitors in its first season. After purchase by a St Louis based company in 1978 the resort acquired neighbour Arapahoe Basin in 1978, at the time allowing it to claim the highest lift-served terrain in the US. Although Arapahoe Basin has been knocked down to third place in the 'highest lifts' league of the US, and is no longer owned by Keystone since the Vail purchase, it is still on a joint lift ticket which also includes other Vail resorts including Breckenridge and Beaver Creek. The Ski The Summit Pass, which was for most of the '90s one of the very few multi-area passes in North America and included Copper Mountain, no longer exists however.

The resort had the biggest terrain expansion in the US for ten years in 1984 when it opened its second mountain, North Peak, adding night skiing the following year. The Outback, the resort's third mountain, was opened as part of a $32 million expansion in 1990. The following year the Alpenglow Stube restaurant, the highest gourmet restaurant in North America, opened.

The other two major events of the 1990s were the announcement of plans to build a $400 million base village in conjunction with Intrawest in 1994 (this has subsequently grown in to a 15 year $1 billion redevelopment plan) and the purchase by Vail in 1997. The on-going spending means that visitors see dramatic change and new dining, lodging and shopping options every season should they choose to visit regularly, and will continue to do so at least until the current plan is completed in 2009.