It was his wife's idea.
The "Star Wars" creator told the Chicago Ideas Week forum on Friday that wife Mellody Hobson, a Chicago native and prominent businesswoman, had enough after four years of what he described as "doodling around" by San Francisco.
"Don't worry. I'll talk to the mayor. I'm sure he'll love it," she told him, according to Lucas.
And she was right. Mayor Rahm Emanuel has publicly embraced the idea, and the Lucas Museum of Narrative Art is set to take its place in the Museum Campus on the city's lakefront.
The filmmaker announced in June that he had picked Chicago.
At the forum this week, he also discussed what the museum will look like.
"It's going to be organic architecture, connected to the ground. And it will look like a living thing," he said in the conversation with interviewer Charlie Rose at the Cadillac Palace Theatre.
Lucas wants a showcase for his collection of popular art, including illustrations by Norman Rockwell, Maxfield Parrish and N.C. Wyeth as well as works by Lucas's visual effects company, Industrial Light and Magic, and other companies.
The museum will also feature art linked to film and digital media, as well as a theatre that will screen films and host lectures and workshops.
Lucas, who has collected art since he was in college, explained that by "narrative art" he means "art that tells a story."
"Illustrative art and narrative art has been short-shrifted," he said. "Critics weren't dealing with narrative art. They were interested in modern."
The city will provide the land, but Lucas said he would bankroll construction and the endowment to maintain it.
"I pay for the whole thing and the endowment, and everything," Lucas said.
"You can afford a museum?" Rose asked.
"Yeah, I can," Lucas answered.