Physical address: 3124 Sonoma Mountain Road, Petaluma, CA, 95954

Mailing address: Post Office Box 750842, Petaluma, CA, 94975-0842

Ranch Phone: 707.996.5049

How to get here: The Mitsui Ranch, owned and operated by the Sonoma Mountain Ranch Preservation Foundation (SMRPF) is located atop Sonoma Mountain at the very end of Sonoma Mountain Road east of Petaluma. We can only be reached from the west (Petaluma) side of the mountain, from Adobe Road. Some search engines and mapping programs will incorrectly indicate accessibility from the Sonoma or Glen Ellen side. Please ignore this because we are only accessible from one route: Adobe Road to Sonoma Mountain Road. To make matters more confusing, there are two Sonoma Mountain Roads that have nothing to do with one another and do not connect. One originates near Glen Ellen off of Warm Springs Road and runs around the north side of the mountain to Pressley Road, just east of Rohnert Park. It’s a beautiful drive, but we cannot be reached from this road. The correct one is described below.

From Highway 101 (north or south) in Petaluma, take the East Washington Boulevard exit and go east off the highway toward the mountains. Proceed 1.8 miles on East Washington Boulevard until you reach a traffic light at Adobe Road. Take a left at the traffic light and drive 0.8 miles north on Adobe road until you see Sonoma Mountain Road on your right. Turn onto Sonoma Mountain Road and drive until you reach the end of the road, which will be at our gate.

Mitsui Ranch gate

SMRPF gate at the end of Sonoma Mountain Road

From the east (coming from Napa), we can be reached by taking Highway 12 to Highway 116, then veering right onto Adobe Road; then to Sonoma Mountain Road.

The ranch is secured by a locked gate and permission is required to enter. Once inside the gate, please take the dirt road which turns left off of the paved road after 0.2 miles (at the top of the incline). The paved road ends at our neighbor’s home and they appreciate their privacy. The SMRPF cottage is 0.4 miles in on the dirt road. Please observe a 15 mph speed limit, and stay on established roads. Thank you.

Veer left onto the dirt road

Left turn sign at the paved/dirt road junction

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  1. Jeff Alvarez
    Feb 26, 2014 @ 17:09:34

    Dear SMRPF Site Manager,

    I have been planning a research project that would include placing different style snake traps in open habitat and measuring the thermal characteristics of those traps, both inside the trap and out. I would require a site where there is some level of security (must leave a laptop on site), and a site that has access to a 110v duplex wall socket to keep the laptop running. Do you think your site would be able to provide these conditions for several days in a row in June or July of this year. If so, I would like to discuss utilizing your site as a research location for my testing.

    Jeff Alvarez


    • Jeff Wilcox
      Feb 26, 2014 @ 17:30:47

      Dear Mr. Alvarez,

      In my opinion, our site would be an optimal location for your research project. Several species of snakes include the yard around our cottage in their home ranges and you can access the duplex socket in at least two locations on the outside of the cottage. If this arrangement would fulfill your requirements, I think you’ll find our site a pleasant and receptive location for your project. We look forward to working with you this summer.

      Jeff Wilcox
      Managing Ecologist


  2. Nathan Keefer
    Mar 17, 2014 @ 20:17:27

    Heaven forbid public access. Did Ms.Mitsui change her mind, which would of course have been her right, or upon her death have you decided to forgo her proposed trail easement, so as to maintain a private albeit not-for-profit playground?
    Nathan Keefer


    • Jeff Wilcox
      Mar 22, 2015 @ 16:37:37

      Dear Dr. Keefer,

      The Mitsui Ranch is open to the public, upon request. We host researchers, college classes, and other groups or persons who have a purpose for being here. Bonnie changed her mind regarding a public trail a few years before her death. She did not make that decision public, as was also her right. She originally made the offer of a public trail provided certain conditions were met by proponents of the trail. After 20 years, those conditions were not met. Knowing her health was failing, she decided to move on and devote the property to researching ways that would help ranchers make a better living; hence the name Sonoma Mountain RANCH PRESERVATION Foundation. I hope that when you peruse the SMRPF website you’ll find that we are devoted to carrying out Bonnie’s vision: that of serious research to perpetuate healthy working landscapes that provide a living for people, and for wild creatures alike.

      Jeff Wilcox
      Managing Ecologist


  3. Pat Eliot
    May 11, 2015 @ 11:03:48

    Jeff: We’ve met at SDC Coalition land use meetings at the Sonoma Land Trust. For further triangulation, I am SLT Wendy Eliot’s mom and a board member of the Sonoma Mountain Preservation. The Sonoma Mountain Preservation Steering Committee meets quarterly to discuss issues that relate to Sonoma Mountain. We would like to invite you to the next meeting on Wednesday, July 15, 2015 , 1:30 –3 pm, to tell us what is happening on Mitsui Ranch and the work of the Foundation. Having just read your excellent website, I can see that lots is happening! We meet at the Sonoma Ecology Center’s headquarters at the Sonoma Developmental Center. I do hope that you will join us. Pat Eliot


    • Jeff Wilcox
      May 12, 2015 @ 11:38:39

      Dear Pat,

      I’d be honored to attend your next meeting, thank you for the gracious invitation.




  4. Adam Boujikian
    Nov 25, 2018 @ 18:59:00

    Good evening, my name is Adam. I work for Henry’s Bullfrog Bees out of winters CA. We currently run around 6,000 hives and are always looking for new properties to place them when they aren’t in crops for pollination. We currently winter a majority of our hives in the Tomales-Petaluma, Dillon beach, Valley Ford and Bodega bay areas. I’m emailing you today to ask if you have ever debated letting a beekeeper pay to place bees on your property? Reading about your operation I believe we could both benefit each other with the symbiotic relationship of pollinators and forage for livestock. Thank you for your time I look forward to hearing back from you and hopefully being able to work together!


    • Jeff Wilcox
      Mar 01, 2019 @ 11:47:19

      Hello Adam,
      Thank you for reaching out. I can’t think of a reason not to host winter bee hives, but since we have many experiments underway, please let me consult with researchers to be sure there are no conflicts and then I will reply.
      All the best,


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