Keith Patterson wasn’t from Texas and hadn’t even spent much time here. Then while living in Los Angeles, a friend said he wanted to do a documentary about Ann Richards. Patterson was familiar with — even a fan of — the late Texas governor, “so I came on board” in late 2010, he says.

The following 20 months, however, have been a journey for the gay filmmaker, who ended up co-directing Ann Richards’ Texas, the documentary that kicks off Dallas VideoFest 25 at the Dallas Museum of Art Thursday night.

“We came to Texas for a year: Austin first, but we ended up everywhere,” he says on the phone from New York, a few hours before his planned arrival in Dallas to attend the festival. “I even have a place in Houston [still].”

Working on the documentary quickly became a passion for Patterson.

“I loved her,” he says. “You can’t get any larger than a Texas politician. That’s why The Best Little Whorehouse is so good — it captures the politics. That song where the governor talks about sidestepping [every issue]? That was [the governorship]. When Ann got in there and started passing a lot of reforms, she shook everything up.”

Richards had help from some powerful friends, including lesbian power couple Lily Tomlin and Jane Wagner, who met and befriended Richards early in her political career. “They were friends from the 1980s when she ran for treasurer and helped write the comedy for Ann’s [historic 1988 Democratic National Conventional] keynote address,” Patterson says. “That’s when she met Dolly [Parton], too. I think Ann was a county commissioner when Dolly was [in Texas] shooting Whorehouse.”

Tomlin, Parton and a host of other celebs offer their voices to the documentary. It wasn’t difficult finding people anxious to talk on the record about the flamboyant Texas pol.

“That was the great part — everybody said yes. We started with interviews with her family, staff and friends first, but people [quickly signed on]. Bill Clinton was kind of the first top gun to agree to an interview. And everybody did a Barbara Jordan impression in their interviews! That would make an interesting series of outtakes on the DVD.”

One of the other boons in his research was how quickly friends and colleagues would share boxes of personal items related to Richards, including photos where she was called an “honorary lesbian” or of Ann alongside her drag queen impersonators.

“I just met a drag queen here in New York who flew down [to Texas] just to participate in an Ann Richards impersonation contest — I’m totally trying to have them show up for the New York screening,” he says.

While Patterson learned a lot about Richards, he learned even more about Texas.

“I think the most surprising thing was she was the last statewide Democrat, and that Texas used to be a Democratic staple,” he says. “It was because of her it flipped from Yellow Dog Democrat. We heard people say Ann was the reason for the modern Republican Party, because conservative Democrats flipped because of her. One of the people we interviewed said the Republicans should build a statue to her.”

Despite that, and despite how many of Richards’ reforms were rolled back once George W. Bush and Rick Perry took over, Patterson was especially proud of Richards’ record on gay rights.

“Obviously she had a lot of lesbian and gay friends. It was the gay baiting thing which was unfortunate — just because she hired gays, they’d say she must be gay,” Patterson sighs.

“She riled people up — she’d go into A&M and appoint a black woman on the board, and their heads exploded. One of my favorite stories was, back in the time when HIV was [still misunderstood], there were a lot of funeral homes who would not take in HIV-positive bodies, or allow them to be shown at sittings. So she appointed a gay guy to the head of the funeral home board. He passed all these rules that said they were discriminating even though they were dead.”

“The reforms she was putting through were from the mindset of women, which was a change, and it’s change that gets the resistance — someone who’s not a good old boy, who doesn’t go along to get along. She got in office to do stuff; when she didn’t get re-elected, she sighed and said she figured she’d help people another way. She was really about helping people,” Patterson says.

Ann Richards Texas screens at 7 p.m. Thursday at the DMA.