Sonoma County Highways

A billboard invites visitors to leave California 37 and explore the fertile Sonoma valley and its many wineries and vineyards. Sonoma County, like neighboring Napa County, is well known for its wineries, and tourists visit the area to sample the many varietals. The turnoff from California 37 east to California 121 north is just beyond the location of this billboard. Photo taken 07/06/13.

Sonoma County, located in the northern Bay Area, is home to some of the most populated areas in this region, including Santa Rosa, the county seat. Home to 483,878 as of the 2010 Census, Sonoma County has several grape-growing regions and wineries, including the well-known Sonoma Valley along California 12. The main north-south corridor through the county is U.S. 101, which connects most of the major cities of Sonoma County. Widening projects have increased capacity along U.S. 101 to allow for carpool lanes in Santa Rosa and bypasses of the cities it serves.

This page profiles some of the roads, highways, and urban city trees within Sonoma County, along with other roads and highways that connect with U.S. 101. Some of the other state routes that serve Sonoma County include California 1 (Shoreline Highway), California 12, California 116, and California 128. We also have a dedicated page to U.S. 101 Business in Santa Rosa.

Mill Street east (Healdsburg)
In Healdsburg, Mill Street serves as the primary route from U.S. 101 south to downtown. This half-diamond interchange also provides access to U.S. 101 north, but access to U.S. 101 requires a trip south on Healdsburg Avenue. Home to 11,254 people as of the 2010 Census, the city of Healdsburg was founded in 1857 by entrepreneur Harmon Heald and incorporated as a city on February 20, 1867. The Northwestern Pacific Railroad was extended to Healdsburg in 1871, shortly after it became a city. Photo taken 07/05/13.
Eastbound Mill Street meets the on-ramp to U.S. 101 north to Cloverdale, Ukiah, and Eureka. Ahead, Mill Street leads into downtown Healdsburg and connects to Healdsburg Avenue south to U.S. 101 south to Santa Rosa. At that intersection, plan to turn left on Healdsburg Avenue north to the downtown square (Healdsburg Plaza) and off-street parking via Matheson Street west or North Street west. Photo taken 07/05/13.
Continuing east, Mill Street meets Healdsburg Avenue (Historic U.S. 101) at the southern edge of Healdsburg. Photo taken 07/05/13.
A small guide sign points the way to U.S. 101 south from Mills Street east via Healdsburg Avenue (Historic U.S. 101) south. Photo taken 07/05/13.
Downtown Healdsburg
The Foss Creek Parkway greenbelt area is located just west of downtown Healdsburg near the downtown parking lot. Walking from the parking lot heading east, we see the Bear Republic brewery. Photos taken 07/05/13.
Healdsburg Plaza is a landscaped park bounded by Plaza Avenue, Healdsburg Avenue (Old U.S. 101), Matheson Street, and Center Street. A plaque within the park acknowledges the history of the area and the approximate location of the original settlement. The final picture shows the gazebo at the center of the well-landscaped park, including the surrounding redwood trees. Photos taken 07/05/13.
Downtown Santa Rosa
Downtown Santa Rosa includes the area surrounding the intersection of Fourth Street, Santa Rosa Avenue, and Mendocino Avenue. Both Santa Rosa Avenue and Mendocino Avenue are part of the old alignment of U.S. 101, and they are designated as U.S. 101 Business through Santa Rosa. Here, we follow Fourth Street east from the vicinity of Santa Rosa Plaza (downtown indoor mall) and Old Courthouse Square, which is situated on Santa Rosa Avenue between Fourth Street and Third Street. The Empire Building, constructed in 1910, is a local landmark and features a well-known clock tower. It is visible on the south side of Fourth Street and west side of U.S. 101 Business/Santa Rosa Avenue. Beyond that is the intersection with D Street, where an old theater was repurposed into a bookstore. Photos taken 07/05/13.
Old Courthouse Square includes both sides of Santa Rosa Avenue (U.S. 101 Business) between Third Street and Fourth Street in downtown Santa Rosa. A fountain and lush landscaping adorn the site. Photos taken 07/06/13.
Third Street west in Downtown Santa Rosa

Now looking at Third Street, this is a major arterial that not only connects U.S. 101 Business/Santa Rosa Avenue in downtown Santa Rosa with U.S. 101 but also travels below the downtown Santa Rosa Plaza mall. This series of pictures follows U.S. 101 west between B Street and U.S. 101 (Downtown Viaduct segment). Photos taken 07/05/13 and 07/06/13.
Third Street passes under the plaza and proceeds under the Downtown Viaduct section of U.S. 101. The next traffic signal connects to Morgan Street north to U.S. 101. After passing under the viaduct, look for a left turn onto U.S. 101 south and California 12 east/west. Photos taken 07/06/13 and 07/05/13.
Turn right from Third Street west to Morgan Street north to Fourth Street or Fifth Street west to Historic Railroad Square. Photo taken 07/06/13.
Westbound Third Street meets Morgan Street at this traffic signal. Turn right here for U.S. 101 north to Ukiah and Eureka. Photo taken 07/06/13.
A guide sign for is U.S. 101 north to Eureka and south to San Francisco is posted on westbound Third Street at the Morgan Street intersection. Photo taken 07/06/13.
A guide sign for is U.S. 101 north to Eureka and south to San Francisco is posted on westbound Third Street at the Morgan Street intersection. Photo taken 07/06/13.
Westbound Third Street next meets Davis Street at this signalized intersection. Turn left here for access to U.S 101/Redwood Highway south and California 12 east/west. Proceed ahead for Third Street; since Davis Street is one-way southbound, no right turns are permitted here. Photo taken 07/06/13.
Third Street east in Downtown Santa Rosa
This view looks to the east on the Third Street tunnel underneath Santa Rosa Plaza in downtown Santa Rosa. Photo taken 07/06/13.
Fourth Street west in Downtown Santa Rosa
A series of stores and restaurants lines the north side Fourth Street between D Street and U.S. 101 Business/Santa Rosa Avenue and Mendocino Avenue. South of here is Old Courthouse Square. Photo taken 07/06/13.
Westbound Fourth Street meets U.S. 101 Business at this traffic signal. Turn left for Santa Rosa Avenue south, or turn right for Mendocino Avenue north in downtown Santa Rosa. In the distance is Santa Rosa Plaza, the downtown indoor shopping mall. Photo taken 07/06/13.
Fourth Street culminates at an entrance to Santa Rosa Plaza, the downtown indoor shopping mall. Another extant section of Fourth Street is on the west side of the plaza as it travels into Historic Railroad Square. The best way to bypass the shopping plaza is to use the Third Street tunnel under the mall. Photo taken 07/06/13.
Fifth Street west in Downtown Santa Rosa
Westbound Fifth Street meets U.S. 101 Business/Mendocino Avenue at this signalized intersection in downtown Santa Rosa. In the distance is the embankment for the U.S. 101 freeway. Photo taken 07/06/13.
Seventh Street west in Downtown Santa Rosa
Westbound Seventh Street meets U.S. 101 Business/Mendocino Avenue at this signalized intersection in downtown Santa Rosa. Photo taken 07/06/13.
College Avenue west (Santa Rosa)
Westbound College Avenue meets U.S. 101 Business/Mendocino Avenue at this signalized intersection in downtown Santa Rosa. Beyond this intersection, College Avenue proceeds west to meet the U.S. 101 freeway. Photo taken 07/06/13.
Morgan Street north (Santa Rosa)
Morgan Street serves as a frontage road to connect to and disburse traffic from the northbound U.S. 101 freeway. The street is located between the U.S. 101 Downtown Viaduct to the left and Santa Rosa Plaza (downtown mall) to the right. Photo taken 07/06/13.
This view looks north along Morgan Street after the Third Street intersection. Photo taken 07/06/13.
The U.S. 101 downtown viaduct spans a city block. Photo taken 07/06/13.
Northbound Morgan Street meets Fourth Street at this traffic signal. Photo taken 07/06/13.
The next signalized intersection along Morgan Street north is with Fifth Street. Turn left for Historic Railroad Square and the California Welcome Center. Turn right for Santa Rosa Plaza, the downtown indoor shopping mall. Photo taken 07/06/13.
Northbound Morgan Street next meets Sixth Street at this traffic signal. Stay left for the reconnection to U.S. 101 (Redwood Highway) north. Photo taken 07/06/13.
Davis Street south (Santa Rosa)
Railroad Square lies on the west side of the U.S. 101 downtown viaduct, while the central business district and Courthouse Square lie on the east side of the freeway. Use Davis Street south to Third Street east to pass under U.S. 101 and the downtown mall to connect to U.S. 101 Business/Mendocino Avenue north and U.S. 101 Business/Santa Rosa Avenue south. (The name change along U.S. 101 Business from Mendocino Avenue to Santa Rosa Avenue actually happens at the Fourth Street intersection.) Photo taken 07/05/13.
The off-ramp to Davis Street immediately brings drivers into the heart of Historic Railroad Square, a shopping and arts district. Restaurants and shops abound in this area; turn right at Fifth Street to get to the welcome center in the old railroad depot. Photo taken 07/05/13.
Davis Street only travels four blocks before returning back onto U.S. 101 south. A small U.S. 101 trailblazer is posted between the Fourth Street and Third Street intersections. Photo taken 07/05/13.
Southbound Davis Street meets Third Street. Turn left here for Third Street east to Old Courthouse Square and the central business district of Santa Rosa. Ahead, Davis Street will merge back onto U.S. 101 south with access to California 12 east/west. Photos taken 07/05/13.
Historic Railroad Square
Historic Railroad Square features various shops and restaurants. One of the centerpiece attractions is the old railroad depot, which now includes a welcome center and museum. The sculptures in the front of the center pay homage to Charles M. Schulz and the characters of the Peanuts comic strip. Charlie Brown and Snoopy are now permanent residents, and Charlie wears a patriotic bandana presumably because of the proximity of the Fourth of July holiday. Photos taken 07/05/13.
U.S. 101/Downtown Viaduct in Santa Rosa

This series of pictures looks at the downtown viaduct in Santa Rosa. The U.S. 101 Downtown Viaduct, a six to eight-lane elevated structure, was originally built in 1968 as a four-lane facility. It was widened in 2009 and carries the above the central business district and separates Santa Rosa Plaza from Historic Railroad Square. This view looks southwest at the northbound side of the viaduct. Public art and foliage help to mask the viaduct; parking is located below the freeway. Some of the views here are from surface level Morgan Street, while views are also available from the Santa Rosa Plaza parking structure. Photos taken 07/06/13.

U.S. Route 101  California State Route 1  Return to the California Gateway

Page Updated September 21, 2013.

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