SOLANO COUNTY, California — About an hour and a half northeast from San Francisco, past Travis Air Force Base and the original Jelly Belly factory, you’ll find one man’s dream. It’s 68,000 acres of farmland, punctuated by windmills and sheep, but in Jan Sramek’s mind’s eye, it’s a bustling city of 400,000 people, about the population of Tulsa, Oklahoma. It has a walkable commercial district, schools, offices, and rows of single-family homes where neighbors enjoy wine on each other’s porches at dusk. If someone—anyone! everyone!—would just agree to let him build it.

He’s been dreaming about this city for at least a decade. “My foundational belief when I started this was that the situation in California would get worse,” Sramek, 38, tells me from the driver’s seat of his Rivian truck. He thought the high house prices across the state would get higher, and that companies would start to leave, because California’s voters had been, in his words, “hoodwinked into this degrowth mind-set.” And so, in 2017, after a short career in business and finance, he started his company, California Forever, which aims to build “the next great American city,” right here in Solano County.

His first move was to spend nine months trying to talk himself out of it—“I tried to prove out that this would fail, because it seemed so outlandish and crazy”—before he decided it was, in fact, a great idea, and went out to investors. “I told them, ‘Hey, you should invest in this crazy thing that no bank or private equity firm or anyone else would touch,’ ” he said. “We should build something spectacular in California—partially as a for-profit investment, but partially as a way of giving back to the state.”...