WCCLS is made up of 16 libraries which are operated by 13 cities and non-profit organizations.
|Aloha Community Library||Aloha Community Library Association|
|Banks Public Library||City of Banks|
|Beaverton City Library||City of Beaverton|
|Beaverton-Murray Scholls Library|
|Cedar Mill Community Library||Cedar Mill Community Library Association|
|Bethany-Cedar Mill Library|
|Cornelius Public Library||City of Cornelius|
|Forest Grove City Library||City of Forest Grove|
|Garden Home Community Library||Garden Home Community Library Association|
|Hillsboro Brookwood Library||City of Hillsboro|
|Hillsboro Shute Park Library|
|North Plains Public Library||City of North Plains|
|Sherwood Public Library||City of Sherwood|
|Tigard Public Library||City of Tigard|
|Tualatin Public Library||City of Tualatin|
|West Slope Community Library||Washington County (Supported by the Friends of West Slope Community Library)|
Past WCCLS-affiliated libraries included ones in the former Tanasbourne Mall (when the Tanasbourne area was unincorporated) and, in the 1970s, Aloha Park Library, located in Aloha Park school, which was open to the public one night a week.
In 2019, the Oregon College of Art & Craft Library closed along with the rest of the college. Additionally, the Tuality Health Resource Center closed in August. These specialty libraries had been affiliated with WCCLS for many years, and some of their collection was distributed to other libraries in the county.
- "Overview of Library Services". Washington County Cooperative Library Services. Retrieved December 11, 2012.
- Gardner, Fran (January 11, 1976). "New network ties together all the county's libraries". The Valley Times. Beaverton, Oregon. p. 10.
- "Library Map and Listing". Washington County Cooperative Library Services. Retrieved January 9, 2016.
- "Aloha Community Library". Washington County Cooperative Library Services. Retrieved January 9, 2016.
The passage of Measure 34-235, the countywide library replacement levy, will allow the Aloha Community Library to become a full member of the Washington County Cooperative Library Services in 2016 and receive operating funds from WCCLS. The target date for this is September 2016.
- "About the Library". West Slope Community Library. Retrieved September 20, 2019.
- "OCAC Distributes Library Assets To Local Institutions". Oregon College of Arts & Crafts Library. Retrieved September 20, 2019.
- "Tuality Healthcare Library to close August 12". WCCLS. Retrieved September 20, 2019.
- "Oregon College of Art & Craft closing in May". WCCLS. Retrieved September 20, 2019.