Portage Glacier is a glacier on the Kenai Peninsula of the U.S. state of Alaska and is included within the Chugach National Forest. It is located south of Portage Lake and 6 km west of Whittier. Portage Glacier was a local name first recorded in 1898 by Thomas Corwin Mendenhall of the United States Coast and Geodetic Survey, so called because it is on …Portage Glacier is a glacier on the Kenai Peninsula of the U.S. state of Alaska and is included within the Chugach National Forest. It is located south of Portage Lake and 6 km west of Whittier. Portage Glacier was a local name first recorded in 1898 by Thomas Corwin Mendenhall of the United States Coast and Geodetic Survey, so called because it is on a portage route between Prince William Sound and Turnagain Arm. Hundreds of years ago the glacier filled the entire Portage Valley, a distance of 14 miles, and was connected to what are now five separate glaciers.