Some of the more interesting, and older, Sonoma County tasting rooms

If you are interested in seeing a bit of California wine history here are some ideas of places to visit in Sonoma County. Some of the history dates back to the earliest days of California; others only a few decades to some of the people that put the area on the premium wine map.

Bartholomew Park
There is a photo exhibit showing the history of the property going back into the 19th century. The winery was purchased and revamped by another local winery family in the 1990s, the Bundschu's (see below).
Extras: Hiking trails on the property.

Buena Vista
California's oldest winery. A visit gives you lots of history plus the new owner has significantly updated the property. The building used for the tasting room dates from the Civil War era.  
Extras: There is a Bubble Room that looks like it's out of 19th century France.

Chateau St. Jean
Built as a mansion in 1920 (there must have been lots of Roaring '20s parties here). It was converted to a winery about 40 years ago. The buildings and grounds are both beautiful and interesting. Skip the regular tasting at the crowded main bar and splurge for the reserve tasting in the cool, old room.
Extras: Nice picnic grounds though you must buy your food and drink from their deli.

Dry Creek Vineyards
Also "only" about 40 years old, but the founder, David Stare, was at the forefront of California wines as his was the first new winery construction in Dry Creek Valley since before Prohibition. And they still make Chenin Blanc!
Extras: Picnic area

Foppiano
A family run winery since Giovanni Foppiano immigrated in 1896. Hopefully, it will stay this way as there's been a bit of a family feud between siblings. Their flagship wine is a Petite Sirah made the old-fashioned way from old vineyards. It might stain your teeth, but it's like opening a bottle of history.

Gundlach-Bundschu
 A 150 year old family winery though it was actually closed down between the San Francisco earthquake in 1906 when they lost their wine to the 'quake and the 1970s when it was started up again by Jim Bundschu. The tasting room is in the old cellar and lab area.
Extras: Cave and vineyard tours are offered. Several events in the vineyards during the summer.

Kenwood Vineyards
In the early 1970s two brothers and their brother-in-law bought the old Pagani Winery (where you brought in your own jug for a fill-up). One of the first Sonoma County premium wineries post-Prohibition. The tasting room in still in the old building and is still funky and unpretentious which can be a nice change. There is a new owner and upgrades are planned. Avoid the grocery store wines and go for the reserves and Jack London Vineyard wines. Prices are reasonable.

Korbel
Founded in the 1880s on an old lumbering site then sold to the current owners in the 1950s. A historic rose garden, redwoods, and a nice tour of the property. It's the best historic tour around. Tasting is in an old brandy facility.
Extras: Deli with indoor and outdoor seating. Tours and tastings are free.

Sebastiani
Started by Samuele Sebastiani in the early 20th century. They were crafty enough to actually continue operation through Prohibition by making sacramental and medicinal wines. Yeah, sure.  :)  It's no longer owned by the Sebastiani family, but is still makes for a historic visit to the town of Sonoma.

Simi
Brothers Giuseppe and Pietro Simi began making wine in 1876 then built the stone cellar that's still in use in 1890. Their daughter, Isabelle, ran the winery from 1904 through 1970! Right after Prohibition ended she opened a tasting room in a large, old Redwood cask that was in use until 1990. In the 1980s winemaker Zelma Long refurbished the winery and put Simi on the map as a premium California winery. Since 1970 the winery has not been in the Simi family. 
Extras: Tours are offered of the old stone cellar.