The Pine Lake Plateau, like most of the Eastside region, was a productive coal harvesting area in the early 20th century. The Grand Ridge Mine, located north of Issaquah at the future site of the Issaquah Highlands, was in operation from 1909 to 1934 and sporadically produced coal until its full closure in the 1950s. The heavily-forested area was partially turned into an undeveloped park by the King County government in the 1960s, and was sought after as a site for suburban development in the late 1970s. The county park was acquired by developer Glacier Park in a land-swap deal for portions of Cougar Mountain and Ravensdale.