A nine mile long island with an average width of one to one and a half miles between Hale Passage and Rosario Strait at the west entrance to Bellingham Bay. In 1791, Juan Francisco de Eliza named it Isla de Pacheco, for the Viceroy of Mexico. Charts of 1792 by Valdes and Galliano used the same name. In 1841, Cmdr. Charles Wilkes called it McLaughlan’s Island, to honor Dr. John McLoughlin, chief factor of the Hudson’s Bay. In 1853, it was named by U.S. Coast Survey, for the Lummi Indian tribe, which once controlled the island, as well as Lopez, Shaw and Orcas islands in San Juan County. Native American names for the island, in two dialects, were Skall-a-ham and Smem-ma-uk.

The Lummi moved onto reservation lands after the signing of the Point Elliott Treaty in 1855. The reservation has a land area of roughly 21 miles, which includes the Lummi Peninsula, and uninhabited Portage Island.