In 1794, Glacier Bay was filled with one massive glacier.

Enter Glacier Bay and you cruise along shorelines completely covered by ice just 200 years ago. Explorer Capt. George Vancouver found Icy Strait choked with ice in 1794, and Glacier Bay was a barely indented glacier. That glacier was more than 4,000 feet thick, up to 20 miles or more wide, and extended more than 100 miles to the St. Elias Range of mountains. But by 1879 naturalist John Muir found that the ice had retreated 48 miles up the bay. By 1916 the Grand Pacific Glacier headed Tarr Inlet 65 miles from Glacier Bay's mouth. Such rapid retreat is known nowhere else. Scientists have documented it, hoping to learn how glacial activity relates to climate changes.

In 1794, as the mother ship H.M.S. Discovery, Captained by George Vancouver, lay at anchor in Pt. Althorp, a survey crew under the command of Lt. Joseph Whidbey painstakingly maneuvered their longboats through the ice-choked waters of Icy Strait.

The remarkably accurate chart the survey produced shows a mere indentation in the shoreline, "terminated by solid compact mountains of ice," where Glacier Bay is today. The great glacier that filled the Bay was by then in rapid retreat, and was the source of the floating icepack that so hindered Whidbey. Any visitor who came by at the glacial maximum, a few decades earlier, would have found the glacier’s tongue extending out into Icy Strait almost to Lemesurier Island.