Internet Archive has several digitized books related to Washington County History and cities in Washington County, Rhode Island.
County Histories generally give information on the settlement of an area, geography, government, and industry in an area, and sometimes include biographical sketches of citizens or other information about the local residents. Some even include genealogies.
Washington County Histories and histories of cities and peoples in Washington County, Rhode Island include:
History of Washington and Kent Counties, Rhode Island, published 1889