Accessible only by boat, Clark Island is a 55-acre marine camping and moorage park with 11,292 feet of saltwater shoreline on the Strait of Georgia. Beaches are sandy on the west side of the island and smooth pea gravel on the east side. This is a popular kayaking site. It provides an important camping and rest site for paddlers traversing the northern San Juan islands.

Boaters anchoring offshore or using the park moorage buoys should be aware of the strong currents on the west side of the island.

The east side moorage area is subject to large waves created by passing commercial shipping in Rosario Strait.

Clark Island was first charted by Spanish explorer Francisco de Eliza in 1791. In Eliza's map, Clark Island and neighboring Barnes Island were named Islas de Aguays after the Viceroy of Mexico.

The present name was established by Charles Wilkes during the United States Exploring Expedition of 1841. Commander Wilkes, an American explorer and naval officer, named the island for midshipman John Clark, who was killed in Perry's Battle of Lake Erie.

Clark Island was briefly homesteaded beginning in the late 1800s before being set aside by the federal government as a lighthouse reservation in 1932. The island was acquired by the Washington State Parks and Recreation Commission in 1964 from the Bureau of Land Management.

A Discover Pass is required for vehicle access to Washington state parks for day use. For more information about the Discover Pass and exemptions, please visit the Discover Pass web page.

The park has 15 campsites, one composting toilet and two vault toilets. Camping is available on a first come, first served basis. The nearest fuel and limited groceries are at Blakely Island Marina. Campsites are open year round. Campsites 1-6 and 14 and 15 accommodate up to eight campers, campsites 7-13 accommodate up to four campers.