Robert Praetzel, a Marin County lawyer who helped put a stop to the Marincello real estate project, has died at age 97.

Mr. Praetzel died of natural causes on Feb. 4 at his home in Kentfield.

Mr. Praetzel was one of the leaders of the 1960s battle that stopped Marincello, a residential and commercial development proposal in the Marin Headlands. The land is now preserved as parkland.

Mr. Praetzel’s wife, Nancy Praetzel, 91, said he would be remembered as a pioneering protector of the county’s open space.

“He was a wonderful man, full of integrity, compassion and generosity, he employed all that as a lawyer,” she said. “His crowning joy was Marincello, but he had a million other things he did.”

Mr. Praetzel, along with his law partner Martin Rosen of Mill Valley, fought back against the planned development funded by Gulf Oil. It would have housed more than 25,000 people on 2,160 acres, Rosen said.

“It was his brilliance alone that was responsible for the creation of the Golden Gate national park district,” Rosen said. “When people walk on the open space of Marin County they should be grateful to a man of talent, vision and perseverance.”

Rosen and Mr. Praetzel led legal challenges that ultimately resulted in the failure and abandonment of the project.

“The headlands and the parklands out there, in my opinion, and Robert’s opinion, are much more important than any city,” Nancy Praetzel said. “We needed to hang on to that little bit of paradise.”

Mr. Praetzel was born in San Francisco in 1925. He dropped out of high school in 1942 to work in the World War II shipyards and enlisted in the Navy in 1943.

He spent his years during the war as a signalman on a tanker that traveled in the South Pacific, delivering fuel to locations as far as South America.

He earned a general educational development diploma and attended College of Marin and UC Berkeley. He then went to UC’s Hastings College of the Law in San Francisco.

Mr. Praetzel later served on many philanthropic, advocacy and conservation boards in Marin.

In an article he published in the Independent Journal in 2017, Mr. Praetzel said he hiked many thousands of miles on Mount Tamalpais and other open space trails for 80 years. In his piece, he advocated for a halt to increased bike access trails on the mountain.

“Tam’s trails were built many years ago by hikers for hikers, and not for bikes,” he said. “They were built so that people could enjoy peace and solitude in a pristine, still wild area. Allowing bikes on a narrow trail would completely destroy that experience.”

Mr. Praetzel is survived by his wife of 66 years; his children Susanna, Matt, Eugenia and Anne Marie; his sister Lola Saylor; his brother Patrick Praetzel; and numerous grandchildren.

A memorial event is pending.