The Washington County Museum (WCM) is one of the oldest historical institutions in Washington County. An independent nonprofit organization, the WCM collects, preserves, and exhibits the history of Washington County, which includes the Tualatin Valley and the western Portland metropolitan area. Its extensive collections have grown over the decades with financial support from county government, local businesses, private sponsors, members, and the work of volunteers. The museum’s archival materials and artifacts, collected since the late 1800s, include 30,400 images, 13,000 artifacts, 25,000 manuscripts, and 1,300 maps. With a staff of between five to eight employees, WCM had about 16,000 visitors, including students, in 2016. 

Washington County Museum had its beginnings in the late 1800s, when the descendants of EuroAmerican resettlers began collecting pioneer-era artifacts such as household items and farm equipment. For years, volunteers built and maintained the museum’s collection. The museum was founded with those collections in 1956 as the Washington County Historical Society, operating out of several locations in Hillsboro as the collection grew. In 1966, WCHS purchased the historic Heidel House in Hillsboro, where the collection and administrative offices were housed. 

The organization was supported by public donations from 1956 until 1975, when the Washington County government began to pay for one full-time and one part-time employee to manage the collection. With support from local businesses, private donations, and the county, the museum purchased and moved into new headquarters on the Portland Community College (PCC) Rock Creek Campus in 1982. Joan H. Smith, executive director from 1982 to 2007, played a primary role in the growth of the institution and expanded financial support, educational programming, and publications.

The Washington County Commission transferred all administrative and financial responsibility to the Washington County Historical Society in 1987 and agreed to continue to contribute funds to manage the collection. In an institutional change to collect and preserve not just historical items but also to promote Washington County’s arts, science, and culture, the historical society changed its name to the Washington County Museum in 2008. Permanent exhibits in 2019 include This Kalapuya Land, and Timber in the Tualatin Valley. The Museum also has a series that features local authors who discuss their research and Washington County history.

The Museum doubled its exhibit and educational space in 2012 when it leased space at the Hillsboro Civic Center. The move allowed for more space at PCC to care for library materials and provided a larger area for exhibits and educational programming. In 2014-2015, WCM reached 11,200 students through its field trips and mobile museum program, largely supported by a grant from the Reser Family Foundation. In the summer of 2017, WCM closed the Hillsboro Civic Center and consolidated its operations back at the PCC Rock Creek Campus. The move was made in an effort to cut costs and centralize collections and programs. 

In 2012, in collaboration with Pacific University library and Centro Cultural of Washington County, the Museum launched Washington County Heritage Online. The website provides public access to over eight thousand images in the collection that focus on Native Americans, historic Hillsboro, commerce and industry, and the Latino community in Washington County.

The Robert L. Benson Research Library, which completed an expansion project in 2015, holds images, oral histories, maps, and manuscripts on such significant people and topics as historian and newspaper editor Albert Tozier, Latino migration history, World War I veterans (Hillsboro Barracks), the Washington County Agriculture Society, the local Daughters of the American Revolution, and the United Spanish American War Veterans.