Located between the Willapa Hills and the western base of Mount St. Helens, Castle Rock is at the heart of Washington timber country in the Pacific temperate rain forest.

Castle Rock is part of the Longview, Washington Metropolitan Statistical Area; the population was 2,446 as of the 2020 census.

The rock formation, resembling a castle, became a geographic landmark for Cowlitz Indians and Hudson's Bay Company traders as early as 1832.

Today, it is the location of The Rock Community Park, with hiking trails, picnic tables, and a historical marker.

[5] Castle Rock is centered primarily on the donation land claim of Eliza and William Huntington, who settled at the location in 1852.

Castle Rock prospered as a Cowlitz River steamboat port and trading center for valley farms.

Sword ferns, common in the region, were picked each year by several hundred people to be processed into medicine.

West Side Highway, running north along the Cowlitz River, connects Castle Rock to Cloud Mountain and the communities of Olequa and Vader, Washington.

Continuing south, West Side Highway / State Route 411 connects Castle Rock to Longview, Washington, and Ocean Beach Highway (State Route 4), putting Castle Rock 75 miles from Willapa National Wildlife Refuge and the Pacific Ocean.

Bus service is provided by Lower Columbia CAP Rural Public Transit to Longview and Castle Rock, via Interstate 5.

On the west side, the trail runs 1100 feet to the Castle Rock Sports Complex.