California State Route 109
state highway in San Mateo County, California, United States
State Route 109 (SR 109) is a short, unsigned state highway in the U.S. state of California. It forms part of University Avenue in San Mateo County between U.S. Route 101 in East Palo Alto and State Route 84 in Menlo Park just west of the Dumbarton Bridge. However, the southern segment within East Palo Alto's borders between U.S. Route 101 and Notre Dame Avenue has never been transferred from the city's control to the California Department of Transportation (Caltrans). Although the route is unsigned, it may be noted on some online maps, including the southern segment still under East Palo Alto's control.
Route description
The unsigned Route 109 is defined in section 409, subdivision (a), of the California Streets and Highways Code, and that the highway is "from Route 84 to Route 101".
SR 109 begins at U.S. Route 101 in East Palo Alto. It continues north until it reaches Notre Dame Avenue, where it then straddles along a north-south city border with Menlo Park. It then enters Menlo Park in its entirety and crosses an abandoned railroad crossing. SR 109 passes by salt evaporators before terminating at SR 84 just west of the Dumbarton Bridge.
The segment of SR 109 in East Palo Alto remains in local control, specifically from US 101 to Notre Dame Avenue.
The public source identifies “California State Route 109” as state highway in San Mateo County, California, United States. This brief keeps that definition visible, then builds a research path around California, State and Route.
Why this record matters
A short description can identify a subject without explaining its stakes. For “California State Route 109”, the useful work is to connect “state highway in San Mateo County, California, United States” to the records capable of establishing context and consequence.
Maps, plans, fabric surveys and administrative records can establish how the site’s name, extent and function changed over time. The source revision retrieved here is dated Sep 7, 2026. The linked authority identifier is Q758046.
A single description cannot reconcile every naming convention, rebuilding phase or administrative transfer associated with a place. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Treat names, boundaries and functions as historically changeable. Maps, plans, inventories and administrative records can clarify what the place meant at different dates.
- Historic place names
- Jurisdictional context
- Routes into maps and plans
Contemporary maps, plans, listed-building records, estate papers and the responsible local or national archive.
Three-step research path
- Establish the record: confirm the title “California State Route 109”, its source revision and the description used here.
- Expand the search: follow California State Route 109 primary sources, California State Route 109 archive and California research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “California State Route 109”?
- Which authority defined the place, boundary or structure at the relevant date?
- Which earlier names or jurisdictions may reveal additional records?
Search terms from this dossier
This entry incorporates text from “California State Route 109” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.