When Californians are designated by gender on a driver’s license, a birth certificate or any state identification, there are only two possible boxes to check: either “M” or “F.”

But they may soon have a third option.

A bill advancing in the Legislature would allow Californians to opt for a “nonbinary” gender marker on all forms of state identification (it’s not yet clear which alphabetical abbreviation will be used, though “X” appears to be a leading candidate). That would make California the first state in the nation to fully depart from the rigid either/or categorization of gender, embracing a more fluid understanding of the term—at least on paper.

Senate Bill 179, introduced by Democratic Sens. Toni Atkins of San Diego and Scott Wiener of San Francisco, has already cleared the Senate and is set to be considered soon in the Assembly Appropriations Committee. The bill would also make it easier for transgender Californians to legally change their designated gender on state documents, including minors who receive parental consent.

“Nonbinary” is a catch-all category that includes those who are intersex (born with a combination of male and female biological characteristics) along with those who feel that neither category male nor female reflect their gender.

The concept has gained cred with millennials, who’ve shown an unprecedented willingness to challenge traditional gender designations. Fusion’s Massive Millennial Poll found that half of millennials—those ages 18 to 34—believe gender is a spectrum and that “some people fall outside traditional categories.” And when it comes to describing themselves, 12 percent of millennials said in a survey for the LGBTQ advocacy organization GLADD that they don’t consider themselves cisgender (a term meaning that their personal identity or gender corresponds to the sex on their birth certificates.)

Should California adopt a nonbinary category, it will still lag far behind Facebook—the social media giant offers users more than 50 custom gender options, including nonbinary, bigender, gender nonconforming, genderqueer and gender fluid.

This June, the state of Oregon’s Transportation Commission agreed to issue a driver’s license with a nonbinary designation for the first time in the United States. California law would go a step further by requiring nonbinary options on all state identification documents. In doing so, California would be the only state to provide this designation in the country, though it follows the lead of countries like Germany, New Zealand, and India.

While so-called “bathroom bill” legislation has placed statehouses in Texas and North Carolina at the frontlines of the nation’s culture war around the question of gender identity, SB 179 has so far enjoyed a relatively peaceful passage through the state Legislature. Despite the not-unexpected objections of conservative religious groups, the bill has so far glided through committees in both chambers with all Democrats, and more than a few Republicans, voting in favor.

Supporters of the bill say the nonbinary marker would allow those who do not identify as either male or female to more easily navigate the tasks of daily life—from making a credit card purchase to boarding an airplane to buying a beer—without subjecting themselves to embarrassment or misunderstanding.

“For someone who has an ID that states a gender that doesn’t match their gender presentation, things can get difficult: everything from a delay in completing what should be a mundane task to outright harassment,” Sen. Atkins said, speaking on the Senate floor last May.

But the bill is about more than convenience, says Dee Shull, who identifies as genderfluid (meaning gender identity varies over time) and uses the pronouns “they” and “them.” It’s also a simple matter of having one’s identity acknowledged and respected.

Dee Shull is fighting for the nonbinary category. Photo courtesy Dee Shull

Dee Shull is fighting for the nonbinary category. Photo courtesy Dee Shull

“It’s liberating to be able to say, ‘yes, this is who I am’ and ‘yes, my state documentation matches that,’ ” they say.

Shull is the communications specialist for the Intersex and Genderqueer Recognition Project, a California nonprofit that bills itself as the first organization in the United States solely focused on helping nonbinary people correct their gender designation on government documents.

“It will take some Californians time to adapt to this,” Shull says. “I’m not expecting miracles, but if I have an ID that accurately reflects who I am, then that’s one less thing that I have to worry about.”

Under current law, anyone who wants to change the gender stated on official state identification documents—either from “M” to “F” or vice-versa—must make a court appearance. They must also receive a doctor’s note confirming that they are undergoing gender confirmation treatment of some kind. That means transgender and gender nonconforming Californians must rely on the availability and moral approval of a medical professional to change a letter on their driver’s license or birth certificate.

Nonbinary people, for whom neither letter applies, must petition the court directly and hope to find a sympathetic judge if they wish to receive nonbinary status—that’s happened on an ad hoc basis a few times.

In the Legislature, opposition has come from predictable quarters. Christian conservative organizations such as the California Family Council and church groups have bemoaned what they call a fundamental redefinition of gender, which they consider to be an immutable characteristic connected to biological traits.

At an Assembly Transportation Committee hearing in July, a lobbyist for the council brought along a copy of the American Heritage College Dictionary to recite the meaning of the word “female.”

“Since the dictionary has not been changed to accommodate this new gender definition, that should be an indication your constituents still believe that gender is based on biology,” Greg Burt said.

But the council has also raised logistical and legal concerns. These arguments, perhaps less vulnerable to the critique that they are motivated by prejudice, have been echoed by some Republican lawmakers in committee as well.

“With all the ID fraud…it seems to me that it would be pretty simple to steal someone’s identity down the line,” Republican Sen. Mike Morrell of Rancho Cucamonga warned the Senate Transportation Committee last April before voting against the bill. He declined to comment for this article.

But Rick Zbur, executive director of Equality California, an LGBTQ advocacy organization that co-sponsored the bill, calls this concern a “red herring.”

“In some ways you could say this bill strengthens procedures to make sure that people’s identities are consistent with who they actually are,” he said. “It’s just about making sure that people’s rights are respected.”