- Glacial erratic boulders of King County are large glacial erratic boulders of rock which were moved into King County, Washington by glacial action during previous ice ages.
- Big Rock is an 8-foot (2.4 m) tall glacial erratic in the city of Duvall.
- A Duvall road, a park, and several businesses are named after it [Big Rock].
- The [Big] rock, and two non-native sequoias adjacent to it probably planted by area pioneers, are a local landmark.
- The [Big Rock] erratic lies in what is said to be the smallest King County park, 20 by 70 feet (6.1 m × 21.3 m) in extent, that barely contains the rock and sequoias.
- Big Rock Park erratic is a glacial erratic in the eponymous city park [Big Rock Park North] in Sammamish.
- Sammamish considered naming the park “Bigger Rock Park” to distinguish it from the identically named park in Duvall.
- Saved from destruction by sit-in conducted by Cascadia College environmental politics students, and relocated away from construction site.
- The rock, which several students occupied during the sit-in, was about 2 meters across before being jackhammered to two thirds its original size.
- 8 by 6 by 4.5 feet (2.4 m × 1.8 m × 1.4 m)
- Fantastic Erratic is a glacial erratic in Cougar Mountain Regional Wildland Park near Bellevue.
- It [Fantastic Erratic] is approximately the size of a two-car garage, and 15 feet (4.6 m) high.
- Four Mile Rock (also Fourmile Rock) is a round granite erratic, approximately 20 feet (6.1 m) across, in the intertidal zone below Seattle’s Magnolia Bluff and 60 yards offshore.
- It [Four Mile Rock] has had a navigational light placed on it and appears on nautical charts.
- Highline College erratic. Granitic with “textbook en echelon dikes”. 21 by 12 feet (6.4 m × 3.7 m) and 9 feet (2.7 m) high.
- Leschi Park erratic in Seattle’s Leschi Park is a sandstone erratic with many embedded bivalve fossils.
- Analysis of the fossils and the rock’s minerals [of the Leschi Park erratic] shows it may have come from the Nooksack Group near Mount Baker, or from the Harrison Lake area of southern British Columbia.
- Ravenna Park erratic in Ravenna Park in Seattle, a granodiorite stone three yards (2.75 meters) tall in Ravenna Creek with a wooden footbridge that wraps around it.
- Talus Rocks, a collection of piled erratics in Tiger Mountain State Forest on Tiger Mountain, forming rock caves (called “Devil’s Dens” in New England) said to be among the largest in Washington.
- Thornton Creek erratic [is] near 17th Ave. NE and NE 104th St., in Seattle Parks’ Kingfisher Natural Area.