First Appearance: Marvel Two-in-One#42 (August, 1978) by writer Ralph Macchio
Purpose: Project: PEGASUS (Potential Energy Groups / Alternate Sources / United States) is a Department of Energy research facility originally designed to explore all possible sources of energy. Among other things, it became one of the world's premiere sites for studying superhuman manipulation of various energy types, and briefly acted as a containment facility for super-powered criminals.
Affiliations: Project: PEGASUS is a subsidiary of the U.S. government, specifically the Department of Energy. It has engaged in scientific and technical exchanges with many organizations including SHIELD, STARCORE, and Stark International. PEGASUS and the Vault cooperated and overlapped in a number of areas, including developing and deploying the Guardsmen.
Base of Operations: Project: PEGASUS' entrance is located atop the Adirondacks' Mt. Athena in upstate New York, and appears to be a fairly high-tech observatory: the visible buildings include two three-story buildings, a cluster of geodesic domes, an observatory, a radio telescope installation, a hangar, a landing strip, and an air control tower. The facility itself is embedded within the mountain, running 24 stories deep. While a steep bluff descends from one side of the facility, below which lies a lake, the other sides are less severe and it is possible to drive to PEGASUS' surface buildings via a moderately steep and winding road, though still sufficiently wide enough to allow a semi to travel it. Project: PEGASUS itself is top secret - the general public is aware of neither PEGASUS' true nature, nor its underground components, though the existence of a facility named Project: PEGASUS is well documented. The town of Pottersville, New York, was located several miles away, but has since been destroyed by Willie Evans (it is unclear if the town has been rebuilt). The current Project:PEGASUS site was occupied by an orphanage from at least the 1930s until the mid-1940s. This was replaced by a government nuclear facilty and research lab from the mid-1940s forward, which eventually became Project:PEGASUS.
Fun Fact: Crates from Project: PEGASUS also appear in the 2010 Iron Man II movie.