High Quality Content by WIKIPEDIA articles! In mountaineering in the United States, a thirteener is a mountain that exceeds 13,000 feet (3,962.4 m) above mean sea level, similar to the more familiar "fourteeners," which exceed 14,000 feet (4,267.2 m). In most instances, "thirteeners" refers only to those peaks between 13,000 and 13,999 feet in elevation.