It is separated from the Lummi Peninsula by Portage Bay and from the central part of Lummi Island by Hale Passage, in Whatcom County.

Portage Island has a land area of 3.803 km2 (1.468 sq mi).

According to the Whatcom County Assessors database, the land and the surrounding tide flats are owned by the Lummi Native American tribe.

The island is wholly contained within the boundaries of the Lummi Indian Reservation.

This Whatcom County, Washington state location article is a stub.