| State: | CA |
| Type: | SR |
| Route: | 242 |
| Map Custom: | yes |
| Map Notes: | SR 242 highlighted in red |
| Section: | 542 |
| Maint: | Caltrans |
| Length Mi: | 3.398 |
| Length Round: | 3 |
| Established: | 1987 |
| Direction A: | South |
| Terminus A: | at the Pleasant Hill–Concord border |
| Direction B: | North |
| Terminus B: | in Concord |
| Counties: | Contra Costa |
| Previous Type: | SR |
| Previous Route: | 241 |
| Next Type: | SR |
| Next Route: | 243 |
State Route 242 (SR 242) is an approximately NaN3.4 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.
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.[1]
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.