# California State Route 128

State Route 128 (SR 128) is a state highway in the U.S. state of California, connecting the Mendocino coast to the Sacramento Valley, through the state's Wine Country. It runs from State Route 1 near Albion to Interstate 505 in Winters.

## Route description

Route 128 begins at Route 1 near the mouth of the Navarro River at the Pacific Ocean. The highway travels southeast and upriver, through the coast redwood forests of Navarro River Redwoods State Park and through the vineyards and apple orchards of the Anderson Valley, to Boonville. Route 253, from Ukiah, has its western terminus into Route 128 at the south end of Boonville. Leaving Boonville, Route 128 climbs out of the Navarro River watershed and crosses the Yorkville Highlands before descending into the Russian River watershed, arriving at Cloverdale in the Alexander Valley, where the highway joins U.S. Route 101 heading south.
A few miles later, at Geyserville, Route 128 separates from U.S. 101 and continues southeast through Knights Valley on the way to Napa Valley, where it joins Route 29 at Calistoga. After passing through the town of St. Helena, Route 128 splits from Route 29 at Rutherford and climbs east over dry ridges above Lake Berryessa to the Sacramento Valley. In Winters, the route's constructed portion ends at Interstate 505. By its legal definition, the route continues 14 mi (23 km) east along Road 93A and Covell Blvd to Route 113 at Davis and then Mace Blvd to Interstate 80, but this segment is currently not constructed.
The section of Route 128 through Navarro River Redwoods State Park is often closed in winter storms due to flooding. Two slower alternate routes are available: the Philo-Greenwood road connects Route 1 near Elk to Route 128 near Hendy Woods State Park, a few miles north of Philo; another alternate route is the Comptche-Ukiah Road, which intersects Route 1 just south of the town of Mendocino and runs inland to Comptche, and departs Comptche on Flynn Creek Road, intersecting Route 128 just up river from the seasonal flood gate closing the highway.
SR 128 is part of the California Freeway and Expressway System, although it is mostly 2 lanes, but except for a small portion in Winters is not 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.

## History

The main road through the Anderson Valley to the mouth of the Navarro River, and from there up the coast to Fort Bragg, was originally called the Navarro Highway; it follows the approximate route of the present Route 128 and Route 1 through Mendocino County. Even earlier, the road followed the Navarro Ridge, to the north of the present alignment, instead of staying at the river level. By 1938, the last stretches of old winding roadway near the present location of Navarro were replaced by a straighter alignment, taken over from a disused logging railway line.
Before being numbered as California State Route 128, the highway was signed as State Route 28. In 1952 it was renumbered State Route 128, permitting a different highway around Lake Tahoe to be numbered as Route 28 to coordinate its numbering with Nevada Route 28.

## Major intersections

Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage. R reflects a realignment in the route since then, M indicates a second realignment, L refers to an overlap due to a correction or change, and T indicates postmiles classified as temporary (for a full list of prefixes, see California postmile § Official postmile definitions). Segments that remain unconstructed or have been relinquished to local control may be omitted. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.
| County | Location | Postmile | Exit | Destinations | Notes |
| Mendocino MEN 0.00-50.90 | ​ | 0.00 | | SR 1 – Mendocino, Fort Bragg, Point Arena | West end of SR 128 |
| Mendocino MEN 0.00-50.90 | Boonville | 29.58 | | SR 253 east – Ukiah | West end of SR 253 |
| Sonoma SON 0.00-24.76 | ​ | ​ | | North Cloverdale Boulevard (US 101 Bus. south, SR 128 Bus. east) – Cloverdale | West end of US 101 Bus. overlap |
| Sonoma SON 0.00-24.76 | ​ | L4.86R53.40 | | US 101 north (Redwood Highway) – Eureka | Interchange; east end of US 101 Bus. overlap; west end of US 101 overlap; US 101 exit 522 |
| West end of freeway on US 101 |||
| Sonoma SON 0.00-24.76 | Cloverdale | R51.62 | 520 | Citrus Fair Drive | |
| Sonoma SON 0.00-24.76 | Cloverdale | R50.43 | 519 | South Cloverdale Boulevard (US 101 Bus. north, SR 128 Bus. west) | |
| Sonoma SON 0.00-24.76 | ​ | R49.05 | 518 | Dutcher Creek Road – Stewarts Point | |
| Sonoma SON 0.00-24.76 | ​ | R47.85 | 517 | Asti (Asti Road) | |
| Sonoma SON 0.00-24.76 | Geyserville | 43.37L4.86 | East end of freeway on US 101 | East end of freeway on US 101 | East end of freeway on US 101 |
| Sonoma SON 0.00-24.76 | Geyserville | 43.37L4.86 | | US 101 south (Redwood Highway) / Canyon Road – San Francisco | Interchange; east end of US 101 overlap; US 101 exit 512 |
| Napa NAP 0.00-34.27 | ​ | 2.66 | | Tubbs Lane – Middletown, Lakeport | |
| Napa NAP 0.00-34.27 | Calistoga | 3.62 | | Petrified Forest Road – Santa Rosa | |
| Napa NAP 0.00-34.27 | Calistoga | 4.5536.89 | | SR 29 north (Lincoln Avenue) – Lakeport, Downtown Calistoga | West end of SR 29 overlap |
| Napa NAP 0.00-34.27 | Rutherford | 24.604.56 | | SR 29 south – Napa | East end of SR 29 overlap |
| Napa NAP 0.00-34.27 | ​ | 7.37 | | Silverado Trail – St. Helena, Calistoga, Napa | |
| Napa NAP 0.00-34.27 | ​ | 11.28 | | Chiles Pope Valley Road – Pope Valley | |
| Napa NAP 0.00-34.27 | ​ | 23.90 | | SR 121 south (Monticello Road) – Napa | North end of SR 121 |
| Solano SOL 0.00-0.75 | No major junctions | No major junctions | No major junctions | No major junctions | No major junctions |
| Yolo YOL 0.00-9.84 | Winters | 8.77 | | Railroad Avenue – Madison, Downtown Winters | |
| Yolo YOL 0.00-9.84 | ​ | 9.84 | | I-505 – Redding, Vacaville | Interchange; east end of SR 128; I-505 exit 11 |
| Yolo YOL 0.00-9.84 | ​ | 9.84 | | CR E6 (Russell Boulevard) – Davis | Continuation beyond I-505; west end of CR E6 |
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus ||||||
* 1 2 3 4 5 6 Indicates that the postmile represents the distance along US 101 rather than SR 128.
* 1 2 Indicates that the postmile represents the distance along SR 29 rather than SR 128.