In the 1921 deed to a Forest Knolls house written by the Lagunitas Development Company to Leonore Walsh, buried among stipulations about sewer systems and liquor sales, the company wrote that the property “shall not be sold, leased or rented to any person not of the Caucasian race.” 

A century later, many deeds in Marin County still contain racially discriminatory language, though such restrictions were rendered unenforceable by a 1948 Supreme Court ruling and became illegal with the passage of the Fair Housing Act of 1968. In a new project, the county is hoping to modify discriminatory deeds and provide opportunities to educate homeowners about the history of restrictive covenants.  

The project, which launched this month, is a collaboration between the Community Development Agency, the Office of the Assessor-Recorder-Clerk and the Office of Equity, which was established last year.

“It’s a partnership. We’re asking homeowners to step forward and share this information with us,” said Tom Lai, director of the Community Development Agency. “You really can’t forge ahead if you don’t understand history.” 

Mr. Lai said the county doesn’t know where these covenants are the most widespread, so the project is relying on homeowners to help map them.

The initiative encourages owners of homes built before 1970 to check their real estate documents for racially discriminatory language and, through a new webpage, report the offensive passages to the county. The county will then modify the deed with a certified document denying the validity of the restriction for future buyers. 

The project came about when Supervisor Katie Rice discovered a restrictive covenant on her own home in San Anselmo. She initiated the project as a way to raise awareness about the county’s discriminatory past. 

“We wanted to find a way to bring awareness to residents about our history and to acknowledge the harm that many of our residents faced when it came to home ownership and their ability to receive equal treatment in housing,” said Leelee Thomas, the county’s planning manager for housing. Ms. Thomas said that her own home in Woodacre, built in 1959, has a restrictive covenant on the deed.

Racially restrictive covenants were never as widespread in rural West Marin as they were over the hill in suburban towns and subdivisions like Greenbrae and Kentfield, said historian Dewey Livingston. But in the San Geronimo Valley, nearly all the parcels had these covenants at one time: The Lagunitas Development Company, which acquired most of the land from Lagunitas to Woodacre from around 1912 into the 1930s, included the restrictions in its deeds. 

San Geronimo Valley historian Owen Clapp said when parcels in the valley first sold in the 1910s and ‘20s, they were very affordable, making room for white people of modest means to move to the area. But because of restrictive covenants, this option was not open to people of color. “A lot of people had the money to do that, but because of redlining they weren’t allowed to,” Mr. Clapp said. 

Discriminatory language like the restriction on the Forest Knolls house was commonplace in the first half of the 20th century, even if it wasn’t always enforced. Some residents found ways around the covenants, selling to people of color off-market, but enforcement often came down to realtors. “The realtors had a lot of power,” Mr. Clapp said. “They didn’t sell lots to people of color.”

A study published last year by researchers at the Othering and Belonging Institute at the University of California, Berkeley found that Marin was among the most racially segregated of the nine Bay Area counties and is home to six out of the 10 most segregated cities in the region. The San Geronimo Valley is among the whitest census tracts in Marin, at roughly 90 percent Caucasian. Mr. Clapp underscored the connection between restrictive covenants and the valley’s contemporary demographic makeup. Housing deeds are one of the major reasons the area is so white today, he argued.

Although restrictive covenants were responsible for much of the initial segregation of Marin, the U.C. Berkeley researchers found that the county’s strict land-use policies perpetuate segregation. Single-family zoning hinders the development of affordable housing, which is a key step to integration. 

“Our land use and patterns of development have also served to further the goals of segregation and these patterns are still evident throughout our communities,” Ms. Thomas said.

The county launched the restrictive covenants program as it stares down the barrel of the Housing Element update, a state mandate to reassess land-use plans to provide more affordable housing opportunities. In early July, the county appealed the state’s latest order to plan for over 3,000 new housing units over the next decade, arguing the number was too high and did not factor in Marin’s unique land-use issues.