If Silicon Valley had an official state park, it would be Castle Rock.

The 5,200-acre preserve, located on Skyline Boulevard at the Santa Clara-Santa Cruz county line, was born when technology pioneer Russell Varian began efforts to purchase the land in the 1950s. Oracle CEO Larry Ellison hiked there with Steve Jobs in the 1990s and discussed plans to remake Apple.

But despite its colorful history, scenic outcroppings and breathtaking views of the Pacific Ocean, Castle Rock always has had a disheveled entryway. Visitors park in a gravel lot and one of the first things they see is a pit toilet.

Now, a Los Altos nonprofit group is trying to make the park more accessible to the public. The Sempervirens Fund is proposing a $7.7 million plan to build a visitor center and a grand entrance, among other features.

The organization hopes to bring more people in to help Castle Rock become financially self-sustaining, in part because of Gov. Jerry Brown’s decision to temporarily put it on the proposed state parks closure list three years ago when he was trying to balance the budget.

“Castle Rock is unique and important. It has amazing rock formations. It’s the gateway into the entire Santa Cruz Mountains,” said Reed Holderman, executive director of the Sempervirens Fund. “We want people to appreciate the park more and the wider redwood ecosystem of the Santa Cruz Mountains.”

The entrance to the park is located in Santa Cruz County. On Tuesday, the Santa Cruz County Board of Supervisors is scheduled to vote on whether to approve the plan.

If the board votes yes, Holderman said, his organization hopes to break ground next summer and finish the first phase — a new parking lot for 90 cars, a picnic area, interpretive exhibits, a 60-seat amphitheater for children, water fountains and flush toilets — by the end of 2015. It plans to eventually transfer the property to state parks along with a $1 million stewardship fund to help cover future operating costs.

Construction would take place on 33 acres adjacent to the existing park entrance. Sempervirens Fund purchased the land in 2010 from the Whalen family, which had owned the property since the 1940s, operating apple orchards and, more recently, a Christmas tree farm. The Christmas trees would be cut down and replaced with madrones, oaks and other native vegetation.

Sempervirens is no stranger to the Santa Cruz Mountains. Without it, many of the area’s ancient redwood forests would have been cut down long ago. In 1900, San Jose photographer Andrew P. Hill, alarmed at how loggers were clear cutting 2,000-year-old redwoods for fence posts and railroad ties, formed the Sempervirens Club, named for Sequoia sempervirens, the Latin name for coast redwood.

The group convinced the state Legislature to purchase 3,800 acres of redwoods near Boulder Creek in 1902 for permanent protection. That established Big Basin Redwoods State Park and began California’s state parks system.

After changing its name to Sempervirens Fund in the 1960s, the organization has preserved more than 33,000 acres in the Santa Cruz Mountains, including most of the land at Castle Rock, Portola, Butano and Big Basin state parks.

The Castle Rock project still faces hurdles, however.

Sempervirens has raised only $2 million of the $7.7 million needed, so it is looking for more donors.

Although there is no organized opposition to the plan, several people have raised concerns at public meetings.

One, Douglas Gunn, is the great-grandson of Duncan McPherson, a former Santa Cruz Sentinel editor who was one of the original advocates for saving Big Basin in 1900. Gunn, who lives on Skyline Boulevard, said the park needs an upgrade, but he thinks a more rustic design and smaller visitor center than the 6,000-square-foot building now planned would be better.

“I don’t see a need for such an extravagant entrance,” he said. “It should be more in character.”

Others with long-standing ties to the area say the park is a unique resource that at least should have a safer entrance area.

Motorists now park along Skyline Boulevard to avoid paying an $8 parks entrance fee. If the new project is build, roadside parking would likely be prohibited.

The park’s boosters say Castle Rock should become a model for other parks’ financial self-sufficiency going forward — and that school children and families coming to it for the first time could learn about forests, wildlife, local geology and history with a decent visitor center.

“By creating a viable entrance, it would make for a more attractive user experience,” said Robert Kirkwood, 75, of Palo Alto.

Kirkwood is a former Hewlett Packard executive. His father, attorney Robert C. Kirkwood, was a California assemblyman and state controller in the 1950s who bought the adjacent Partridge Farm property in the 1940s to grow pears and apples. The younger Kirkwood has donated $1.5 million toward the Castle Rock project.

“It would be great if more people would be able to experience the kind of joy that we had as kids there, scrambling around in those hills and climbing the rocks,” he said. “It was great fun.”

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN