THE RESEARCH DIRECTORY
Follow the sources.
A starting collection of route histories, preservation projects, and historical map archives for California and Oregon.
These independent resources provide context and research leads. Their maps and accounts should be checked against dated records when reconstructing a specific alignment. Links reviewed October 2026.
California history & preservation
Historic Highway 99 Association of California
A California routing overview, with links to preservation work, regional features, and the association’s broader history resources.
California Highways — Route 99
An extensive reference on Route 99, including historical routing, legislative context, and links to further research.
SoCalRegion — Virtual Tour of US 99
A photographic tour and historical notes covering portions of the former highway. Useful for connecting route history with identifiable places.
Ridge Route Preservation Organization
History of the original Ridge Route and its successors, from an organization dedicated to the historic road’s preservation.
Oregon history & routes
AARoads — Route 99 and Historic US 99
An introduction to Oregon’s 99 corridor, with route descriptions and road photographs.
ODOT — History & historical maps
An official starting point for Oregon transportation history, including links to digitized state highway maps and other archival resources.
State Library of Oregon — Digital Collections
Search Oregon government publications and historical collections. Follow ODOT’s map links or search by highway, location, and year.
Historical maps
USGS topoView
Browse and download historical topographic maps by location and edition. These can help identify older roads, bridges, and terrain when researching an alignment.
Keep a useful research record
Record the map title, publisher, edition or publication date, relevant location, and permanent source link. Keep the evidence for a route line alongside the line itself.
Links do not grant permission to reproduce photographs, maps, or written material. Credit each source and check its reuse terms before including material in the archive.