Walter Cottle Lester could have been another Silicon Valley millionaire. He was in the right place at the right time with something highly marketable. Potential investors swarmed. How much would it take, they asked — $100 million? $500 million? It turned out that Mr. Lester had a different kind of investment in mind. 

 Walter Cottle Lester’s farm serves to educate the public about the Santa Clara Valley’s heritage. Santa Clara County Parks

He owned 300 acres on the southern side of San Jose, one of the last large expanses of farmland in a dense and very expensive real estate market. Instead of selling to a developer who would build yet another housing subdivision for high-tech workers, Mr. Lester held out for a low-tech dream: He wanted the land to stay the way it was, preserved as farmland and open space, with arching old oaks and broad views of the surrounding mountains, not just strip malls.

On Feb. 1, the day after Mr. Lester died at age 88 in San Jose, that vision began coming to fruition: The first phase of Martial Cottle Park, named for Mr. Lester’s grandfather and long in the planning, opened to the public in the form of a four-mile trail on the property. 

 Mr. Lester with his dog. He started farming in the 1940s. Craig Giordano

The project eventually will include a visitors’ center, picnic areas, historical farming exhibitions and the leasing of some of the land for farming, but — at Mr. Lester’s insistence — no ball fields, swimming pools or playgrounds. Santa Clara County will oversee the park, though part of it is owned by the California Department of Parks and Recreation. A county parks fund, approved by voters, will pay the $26 million in construction costs.

“I wouldn’t call him a hermit,” Mr. Giordano said, “but he was maybe a borderline recluse.”

One of the structures being preserved as part of the park is the Victorian house where Mr. Lester died. It is also where he was born, on July 7, 1925, and where his grandfather lived and his mother, Ethel, was born in 1891.

Mr. Lester has no immediate survivors. He never married and did not have children. Neither did his only sibling, his sister, Edith. They lived together in the Cottle house. When Edith died, in 1999, Mr. Lester received a stunning estate tax bill, in the tens of millions of dollars. Planning for making the property into a park was already underway, and the state helped pay part of the tax bill.

In 2003, Mr. Lester signed a grant deed formally transferring the property.

“No part of the property shall be used for high intensity, organized recreational uses such as athletic fields, playgrounds, tot lots, swimming pools, play courts, amusement rides or similar uses, nor as a repository for historic structures that are relocated from other sites,” the deed reads in part.

“The property shall be used as a public historical park that informs and educates the public about the agricultural heritage of Santa Clara Valley, as exemplified by the Martial Cottle family, dating from the 1850s into the 20th century.”