Margerie Glacier is a 21-mile-long (34 km) tide water glacier in Glacier Bay in Alaska and is part of the Glacier Bay National Park and Preserve. It begins on the south slope of Mount Root, at the Alaska-Canada border in the Fairweather Range, and flows southeast and northeast to Tarr Inlet. The glacier was named for the famed French geographer and geologist Emmanuel de Margerie (1862–1953), who visited Glacier Bay in 1913. Margerie Glacier is one of the essential features of Glacier Bay, which was declared a U.S. National Monument on February 26, 1925, a National Park and Wild Life Preserve on December 2, 1980, a UNESCO declared World Biosphere Reserve in 1986 and a World Heritage Site in 1992. While most of the tidewater and terrestrial glaciers in the Park are thought to be thinning and receding over the last several decades, Margerie Glacier is thought to be stable and nearby Johns Hopkins Glacier is stated to be advancing, on the eastern face of the Fairweather Range. Margerie Glacier can only be visited by ship or seen by air and access is limited by the National Park Service.