Starting March 1, all single-occupancy bathrooms in businesses, government buildings and public places must be open to people of either sex and display distinctive “all-gender” markings.

The change comes from a new state law meant to increase access to public bathrooms for transgender people and women. It was adopted in the wake of controversial legislation in North Carolina restricting bathroom use to a person’s birth gender.

“This addresses a whole segment of society that has been marginalized and feels like they are not included,” said Rick Dean, executive director of the Santa Rosa nonprofit HIV test center, Face to Face, whose clients include gay and transgender people. “It addresses it squarely and says, ‘We get it. Not a big deal.’ ”

The law, AB1732, was sponsored by Equality California, the Transgender Law Center and California NOW, and written by Assemblyman Phil Ting, D-San Francisco.

It allows people to use the public, single-stall bathroom of their choice, regardless of gender identity. Bathrooms used by more than one person at a time are exempt.

It sailed through the state Legislature despite concerns about costs to small business and what’s been called the “pee seat” — the sometimes wet toilet seat women sharing bathrooms with men might encounter. The only organized opposition came from the California Right to Life Committee.

It was signed by Gov. Jerry Brown in late September.

Since then, local businesses, schools and government agencies have been working to comply, an act that merely requires changing exterior bathroom signs. No other modifications must be made.

Potentially thousands of public bathrooms across the North Coast could be affected.

At the Sonoma County government center, workers have installed about 30 of the blue-and-white signs featuring silhouettes of a man and woman at a cost of about $200 each, said Caroline Judy, director of General Services.

Many more will be put up in other departments including the main jail, the Hall of Justice and the Family Justice Center.

She said the job would be finished by March 1.

“Basically, we’re working hard to make sure the county is compliant with the law,” Judy said.

Santa Rosa officials also were working to change 137 signs in city buildings from fire stations and park facilities. City costs were not available.

Local businesses, many of which already offer gender-neutral bathrooms, are making the change without controversy. A manager of Santa Rosa Chamber of Commerce said she was unaware of any concern over the new law or its requirements.

“There hasn’t been any conversation I’ve been privy to at all,” Chief Operating Officer Debbie Gesualdo said.

Advocates were pleased with the apparently widespread acceptance of AB1732.

Jason Howe, an Equality California spokesman, said it will provide equal access to women and gay people who have faced inconvenience and harassment under the old way of doing things.

“It’s interesting that as North Carolina is doing back flips to preserve its law, California is moving in the opposite direction with a minimum amount of debate,” Howe said.