The government closed the quarry in 1969 and its owner ordered the workers and their families to leave, expecting to sell the property as part of the upscale suburb Bosques de las Lomas.

But the families were helped by wealthy parents whose daughters attended a nearby convent that had opened a primary school for the workers’ children. Several parents had the ear of leading city officials.

At the same time, an activist priest, the Rev. Rodolfo Escamilla, infused with liberation theology, began to organize the community as a co-op.

He was murdered in 1977; his killers were never found. A mural of the priest adorns a wall in Palo Alto, which celebrates his birthday every year.

After two years of negotiations with the authorities and a face-off with the landowner — whose claim was tenuous, Mr. Ortiz said — the city seized the land.

One summer night, Caratina García, then a mother with two young children, and a few other women stood up to the police who had been sent by the quarry’s owner. “They threw tear gas, but even then they couldn’t remove us,” said Ms. García, now 67. “They never came back.”

“We had the right” to the land, Ms. García said. “We had been paying rent all along.” Somewhere in her tidy room she still has all those rent receipts.