The area around Glacier Bay in southeastern Alaska was first proclaimed a U.S. National Monument on February 25, 1925. It was changed to Glacier Bay National Park and Preserve in 1980 by the Alaska National Interest Lands Conservation Act. Glacier Bay National Park and Preserve is a United States National Park in the southern part of Alaska west of Juneau. The park area was included in an International Biosphere Reserve in 1986 and is part of a UNESCO World Heritage Site. The park covers 5,130 mi² (13,287 km²). Most of the park is a designated wilderness area which covers 4,164 mi² (10,784 km²) of the park.
No roads lead to the park and it is most easily reached by air travel. During some summers there are ferries to the small community of Gustavus or directly to the marina at Bartlett Cove. Despite the lack of roads, there are over 300,000 visitors per year, most on cruise ships.
Glaciers descending from high snow capped mountains into the bay create spectacular displays of ice and iceberg formation. In the last century the bay’s most famous glacier was probably the Muir Glacier, at one time nearly 3 km (2 miles) wide and about 80 m (265 feet) tall. The Muir Glacier has receded and since the 1990s is no longer tidewater. Most visitors today see the Margerie and Lamplugh Glaciers. All of Glacier Bay was glacier-bound as recently as 1750.
The explorer Captain George Vancouver found Icy Strait, at the south end of Glacier Bay, choked with ice in 1794. Glacier Bay itself was almost entirely iced over. In 1879 naturalist John Muir found that the ice had retreated almost all the way up the bay, a distance of around forty-eight miles. By 1916 the Grand Pacific Glacier was at the head of Tarr Inlet about 100 km (65 miles) from Glacier Bay's mouth. This is the fastest documented glacier retreat ever. Scientists are hoping to learn how glacial activity relates to climate changes from the retreat.
Glacier Bay National Park and Preserve includes 9 tidewater glaciers. 4 actively calve (shed) icebergs into the bay.