Keystone Resort is the largest ski resort in Summit County located in Keystone, Colorado, United States. It was founded on November 21, 1970 by Max Dercum. The resort is owned and operated by Vail Resorts which also operates three other resorts in Colorado (Vail, Beaver Creek, and Breckenridge), three in the Lake Tahoe region (Heavenly Ski Resort, Northstar at Tahoe and Kirkwood Mountain Resort), Mt. Brighton in Michigan, Canyons in Utah, and Afton Alps just outside of the St.