MapofUS.org, WorldAtlas.com and Geology.com have well-drawn maps of Oregon showing county lines. Each site offers unique features. For example, WorldAtlas.com displays a list of counties, cities and area codes beneath the state map with links to map of each county.
Geology.com offers quick and clear maps that allow the user to display options including satellite imagery, latitude and longitude, highways, and resources. It also offers physical, road atlas and topographical options. MapofUS.org is geared to historical research. Among other features, it shows the counties as they formed and each state as it developed on a year-by-year basis from the 1800s until 1975.