At the top of London Ranch Road, Jack London State Historic Park charges $15 a vehicle and keeps its gates open from 9 a.m. to 5 p.m. Over the ridge on the old Sonoma Developmental Center land, State Parks lists its SDC Open Space events with a plain line: "Park does not charge for entry." Visitors there park along Harney Road and walk in past a metal gate.
Those two properties are now headed toward becoming one park. On Oct. 14, California State Parks announced that its Bay Area District supervisors and Jack London Park Partners had filed paperwork to amend the Jack London State Historic Park General Plan to include 765 acres of SDC Open Space. That would bring the combined park to more than 2,200 acres. The bigger map is still a planning document. For anyone walking these trails between now and the holidays, the two halves still work differently, and those differences decide where you park, what you pay and whether the dog can come.
What the filing does, and what it leaves alone
The amendment adds the acreage on paper without merging how the land is run. In the State Parks announcement, Jack London Park Partners keeps running the historic park and State Parks staff keep running the 765-acre SDC Open Space.
This step was planned from the start. The State Parks SDC Open Space page has said all along that the open space would "eventually be incorporated into Jack London State Historic Park through a public General Plan process." The agency's phase plan calls for public input, stakeholder engagement and tribal consultation on the way to the General Plan Amendment, with improved access and facilities coming once the plan is put into effect. The October announcement gives no dates for a comment period or public meeting.
Some of the land around the trails is not part of this at all. Both lakes on the property stay with the local water district as drinking-water sources. The core campus buildings along Arnold Drive are set aside for future housing and retail, and CAL FIRE is receiving a portion of the southeast property for a new facility. State Parks has also said that, at first, access to the property will not change.
Two front doors, two sets of rules
Here is how the two halves compare this fall, using the most recent posted information from each operator.
| Jack London State Historic Park | SDC Open Space | |
|---|---|---|
| Day-to-day operator | Jack London Park Partners | California State Parks staff |
| Entry | $15 per vehicle since June 1, 2026 | Listed as "Park does not charge for entry" on its events |
| Where you start | 2400 London Ranch Road | Public parking along Harney Road, then on foot past the eastern metal gate to Sunrise Road |
| Posted hours | 9 a.m. to 5 p.m. daily, closed Dec. 25 | No separate schedule posted |
| Dogs | Not covered by the sources here | Leashed on paved roads only, not on trails |
The SDC side also comes with standard State Parks rules. Fishing and swimming are prohibited in both lakes because they are water supplies. Gathering downed wood is not allowed, and smoking is permitted only on paved roads and in parking areas.
The dog rule draws the map on the SDC side
For anyone walking with a dog, the dog rule matters more than any other. Dogs must be on a leash no longer than six feet. Except for service animals, they are prohibited on all SDC trails and allowed only on paved roads.
That rule points dog owners to the eastern side of the property. State Parks describes the Sunrise/Baker loop as a flat walk of 45 to 50 minutes with slight elevation changes and light shade. Its paved route circles a seasonal wetland and passes the old SDC farm, horse corral, dairy, maintenance buildings, sewage treatment plant and soccer field. That part of the campus once handled the animal husbandry and facilities work that made the center largely self-sustaining. State Parks also runs this route as its Accessible History Hike.
The calendar follows the same logic. State Parks launched its B.A.R.K. Ranger program at SDC Open Space on Aug. 22. Dogs and their owners learn the rules at a pop-up tent, take a walk, then come back to recite the B.A.R.K. Ranger Oath. Dogs that complete it earn a wooden badge and a Polaroid with their owner. The Halloween Costume B.A.R.K. Ranger Pop-Up is Saturday, Oct. 31, from 9 a.m. to noon near Sunrise and Baker Road. Halloween-themed prizes go to dogs in costume, and the newsletter says to park along Harney Road and walk past the eastern gate.
Where the unpaved trails go
Without a dog, the SDC side opens up. The Lake Suttonfield route that State Parks interpreters lead is about 2.5 miles of unpaved trail. It is rated easy to moderate with slight elevation changes, and the guided version takes at least an hour and a half. This summer, State Parks and CAL FIRE graded the Suttonfield Lake fire roads between Sunrise Road, Sonoma Valley Regional Park and the CAL FIRE station to improve access through the summer and fall.
Farther west, the two parks already share a trail. The Press Democrat reported that Orchard Road runs from the center of the SDC campus past the cemetery and Fern Lake to the historic orchard, with Jack London State Historic Park and the Wolf House ruins beyond. Camp Via, the center's former overnight camp, transferred to State Parks in 2024 and is open for hiking, biking and horseback riding.
The longest walk on the fall calendar covers both properties. "Sonoma Ridge in Sonoma Developmental Center/Jack London" is a free, Spanish-guided intermediate hike on Sunday, Nov. 15. The Sonoma Valley listing puts it at 9.67 miles with 2,126 feet of elevation gain, requires reservations and gives the meeting point as Arnold Drive and Harney Road inside SDC.
The calendar through Nov. 22
Most of the programming on the historic park side centers on the House of Happy Walls Museum. Fees vary by event, and the Amy Tucker talk waives park entry, so it is worth checking each listing before you drive up London Ranch Road.
- Friday, Oct. 30, 5:30 to 7 p.m.: Cuando Cae la Noche, a free Spanish-language evening walk at Jack London State Historic Park that includes watching the park's bat colony emerge.
- Saturday, Oct. 31, 9 a.m. to noon: Halloween Costume B.A.R.K. Ranger Pop-Up at SDC Open Space, near Sunrise and Baker Road.
- Through Friday, Nov. 6: two Día de Muertos ofrendas at the House of Happy Walls Museum. One honors Jack and Charmian London, and the other is open to community contributions.
- Friday, Nov. 6, 11 a.m. to 12:30 p.m.: Amy Tucker's "Hunting for the Snark Illustrations" talk in the museum, $15, with park entrance waived.
- Sunday, Nov. 15, 2 to 3:30 p.m.: an Author's Afternoon with Marlo Faulkner. The program is free with a reservation, and the $15 vehicle entry applies. The same morning, the Sonoma Ridge hike starts on the SDC side.
- Sunday, Nov. 22, 10:30 a.m.: the memorial for the 110th anniversary of Jack London's death. Participants meet at the museum for a half-mile walk to the grave. It is free, and the $15 vehicle fee applies.
The campus in the middle
The trails surround a campus that is moving on a slower timeline. The Sonoma Index-Tribune reported in August that the latest proposal calls for 990 homes, 130,000 square feet of commercial space and a 150-room hotel on the 180-acre core. An Aug. 28 update posted by Eldridge for All says the Draft EIR will not be released in 2026 because additional technical and environmental studies extended the schedule.
The Index-Tribune also reported that the site was found compliant with county fire codes on Oct. 5, after hydrants were restored. Temporary fencing went up around some damaged buildings and areas under soil and water testing, and Permit Sonoma said it was not expected to block public access to the adjacent open space.
State Parks wants to hear from people who use the open space. On Oct. 16, it posted an SDC Open Space Visitor Survey on its news and updates page. The results will help decide what interpretive programming the property offers next.
Open space at Eldridge's edge and a campus with no release date for its environmental review both affect what nearby Glen Ellen property is worth. Del Fava Parker has watched this stretch of Arnold Drive for decades. If you own near the SDC lands and want to know where your property stands while the park and the campus take shape, request a home valuation and we'll go through it with you.
