California State Route 242
state highway in Contra Costa County, California, United States
State Route 242 (SR 242) is an approximately 3.4-mile (5.5 km) state highway in Contra Costa County, California that links Interstate 680 at the Pleasant Hill–Concord border to State Route 4 in Concord. Along with Interstate 580, State Route 24, Interstate 680 and State Route 4, it serves as the most direct route between the San Francisco Bay Area and the Sacramento–San Joaquin River Delta region.
In 2000, State Route 242 was widened to six through-traffic lanes for the entire route. Ramp metering is present at all onramps, and is used southbound in the morning and northbound in the evening. It was signed as part of State Route 24 until ca. 1987.
Route description
Route 242 is defined in section 542 of the California Streets and Highways Code, and that the highway is "from Route 680 to Route 4 north of Concord".
The route begins as a freeway at Interstate 680 at the Pleasant Hill–Concord border. It then heads north into Concord, meeting Clayton Road, Concord Avenue, Grant Street, and Olivera Road before meeting its north end at State Route 4 just west of the former Concord Naval Weapons Station.
SR 242 is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.
This brief starts where responsible research should: with the source description of “California State Route 242” as state highway in Contra Costa County, California, United States. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the places & architecture register because the source frames it as state highway in Contra Costa County, California, United States. Its deeper value depends on whether names, dates, institutions and citations support that framing.
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 Jul 19, 2026. The linked authority identifier is Q758175. Authority coordinates are 37.981, -122.042. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 2000 and 1987.
Architectural summaries often privilege surviving fabric and can understate demolished phases, contested use or displaced communities. 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 242”, its source revision and the description used here.
- Expand the search: follow California State Route 242 primary sources, California State Route 242 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 242”?
- What physical evidence or contemporary plan supports the description?
- Which authority defined the place, boundary or structure at the relevant date?
Search terms from this dossier
This entry incorporates text from “California State Route 242” 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.