MARTINEZ >> Just a mile from the historic home of revered naturalist John Muir lies the kind of scenic wilderness he spent his life fighting to conserve — 297 acres of a grassy, oak-covered ridgeline landscape known as the Alhambra Hills.

For more than a decade, Richfield Real Estate Corp. has held onto city permits that allow it to build 109 single-family homes on 70 acres of the property on the southern edge of town. But instead of building, the Texas-based property manager held off for myriad reasons over the years and agreed in March to sell the land to the city for $19.25 million so it can be preserved permanently.

To raise that kind of money, the city has placed a property tax measure on the June 7 ballot. If Measure F is passed by a two-thirds vote, owners of single-family parcels would pay $79 a year and those of nonresidential properties from $150 to $600 over the next three decades.

While the tax is estimated to generate $20 million during that period, city officials hope environmental groups could chip in the differenceif the actual amount falls short of the sales price for Alhambra Hills.

If the measure fails, Richfield says it intends to proceed with development.

To those who support the measure, the decision to conserve Alhambra Hills for generations to come is a slam-dunk.

“It’s really a magical view up there, a stunning ridge,” said Councilman Mark Ross, who often visited the area as a child. “The way the forest parts into the open California grassland — that’s really special.”

Ross said if residents approve the tax measure, the city would turn the ridgeline property into “the greatest central park a city could have on the West Coast.”

The land also holds historical significance because some of it apparently once belonged to Muir, according to Martinez resident Jamie Fox, who leads the Save Alhambra Hills Open Space committee

Fox, a Google electrical engineer, said he tracked down a U.S. National Park Service map in 2014 that revealed Muir owned property on the ridgeline in the 1800s.

With help from Muir’s great-grandson, he brought the map to city officials, who hadn’t known about the history when they oversaw Richfield’s 300-page environmental impact report years earlier.

“This is not just a city issue,” Fox said. “This is a national historic site, and we can’t let it be destroyed. It’s too special.”

Stephen Nussbaum, Richfield’s director of asset management, said the company in “good faith” gave the city the time it needs to buy the property.

“If Measure F fails we intend to proceed with the approved project,” Nussbaum said in an email, explaining that Richfield has already invested millions of dollars since buying the property.

Richfield has been trying to get the project off the ground since the early 1990s, when it initially won the city’s approval for a much larger development of 212 homes on 122 acres.

Back then, environmental groups got involved and pointed out the ridgeline serves as a habitat for the threatened Alameda whipsnake. In the face of opposition, Richfield backed off and agreed to downsize the project’s scale.

Richfield subsequently discovered that building homes on the steep hillside would be much more expensive than anticipated, and a once-stable housing market that turned volatile in the late 2000s didn’t help.

By the time Richfield came back in 2011 seeking approval for the downsized development and promising to create a public trail network on the rest of the property, city officials didn’t want to see any homes built along the ridgeline.

But city officials felt their hands were tied because the area has been zoned residential since the 1970s and Richfield had already agreed to cut the number of homes by more than half to mitigate potential environmental impacts such as harming the whipsnake.

So the council, with Ross dissenting, approved permits for the 109-home development. Several council members made it clear they did so to avoid a potential lawsuit.

Asked why the council had turned sour on the development after once being for it, Ross said the original approval came “well before the value of pure open space was realized by communities and legislative bodies. Soon, it was, ‘Hey, this (development) is really ugly.’ I’m in real estate, it’s my industry, and I can tell you this is a significant visual detriment to many parts of Martinez.”

No organized opposition to Measure F has surfaced yet, Ross said. “The public has come to understand the value of the environment,” he surmised.

“That’s been a gradual learning curve,” he added. “Open space is the most obvious, because unlike global warming, you can see the subdivision on this hill forever. It’s a glaring environmental issue.”