East Mountain in Essex County, Vermont, rises in the Northeast Kingdom south of Seneca Mountain within the Connecticut River watershed, with its slopes draining into brooks and streams that ultimately feed the Connecticut and Passumpsic rivers. Beyond its geography, the mountain briefly served as the site of a Cold War radar installation. Built in 1955 as North Concord Air Force Station, renamed Lyndonville Air Force Station in 1962, and closed in 1963, the facility linked the mountain to an unusual episode in UFO lore when station personnel reported an unidentified flying object sighting in 1961, shortly before the reported Barney and Betty Hill abduction.