Historic maps can be very useful in developing the history of a site. Many online resources provide access to online scans of historic maps. Some that you may find useful are listed below:
USGS Topo Maps
Current and historic USGS topographic maps can be viewed at the USGS Map Locator and Downloader
NOAA Historical Map and Chart Collection has scans of old coastal charts and navigable rivers such as the Columbia.
The Aerial Photography Collection has over 600,000 aerial photographs of Oregon, stretching as far back as the 1920s. You need to request to see these in advance. Fill out the Academic Request form. We will contact you when the photographs are available for you to view in the library. Aerial photographs do not leave the library, but scanners are available for your use.