Pacific Tarn is a small glacial lake on the broad eastern ridge of Pacific Peak in Colorado’s Tenmile Range, high in the Rocky Mountains. At 13,420 feet above sea level, it is the highest lake in the United States with a name officially recognized by the United States Board on Geographic Names. Unnamed until the early 21st century, it gained official status after Carl Drews of Boulder led a 2002 expedition to measure the lake. The board approved the name on January 8, 2004. Later scientific and exploratory interest included the first scuba dive there on September 7, 2013.