MISSOULA -- The groom runs a city of 765,000 people. The bride is an aspiring actress from West Hollywood.

Together they'll stage Montana's celebrity wedding du jour this summer at her family's ranch near Victor.

Gavin Newsom, the dashing young mayor of San Francisco, and aspiring actress Jennifer Siebel have set their wedding date for July 26, the San Francisco Chronicle reported this week.

Invitations to 250 guests have been sent, and California Sen. Dianne Feinstein and her husband, Richard Blum, hosted a wedding shower for the couple Saturday night.

"It's going to be a very natural, Big Sky-type of event," said Stanlee Gatti, a close friend of Newsom and a "high society party planner," according to the newspaper.

"It's always been (Siebel's) dream to be married at the ranch. It has always been a very special place for her," Gatti added.

Siebel's father Ken, an investment manager in the San Francisco area, and his wife Judy bought the Bitterroot Springs Ranch at Bell Crossing nearly 30 years ago.

Ken Siebel is a second cousin to software entrepreneur Tom Siebel, founder of the Montana Meth Project and owner of working ranches near Grass Range and Wolf Creek.

In a 2007 interview with the international fashion magazine, Lucire, Jennifer Siebel recalled her family's first visit to what would become their Montana ranch.

"It was pure heaven -- an old cattle ranch that since then we have nurtured back to health and which serves as a home for not only teems of wild flora and fauna but several farm animals," she said. "It's probably my favorite place on this planet aside from eastern Africa's open plains and Botswana's Okavango Delta."

Siebel, 33, is a Stanford graduate who has been involved with the environmental group Conservation International since childhood. She has never been married, but helped fill columns in the tabloids a few years ago when she dated actor George Clooney.

Her acting resume includes two recent movie releases, "The Trouble With Romance," which she co-produced, and a makeover of the horror flick "April Fool's Day" that went straight to video.

She also appears in a recurring role on the NBC drama series "Life." Siebel is involved in Women's Independent Cinema, which distributes DVDs that honor female filmmakers, writers and composers.

This will be the second celebrated marriage for Newsom, 40, who has been called one of the Bay Area's most eligible bachelors. He wed Kimberly Guilfoyle in a lavish ceremony at St. Ignatius Church in San Francisco in 2001. The reception was hosted by billionaire philanthropists Gordon and Ann Getty.

Newsom and Guilfoyle were divorced in 2006. Guilfoyle has remarried and hosts "The Lineup" on Fox News in New York.

Newsom became San Francisco's youngest mayor in 100 years when he was elected in 2003. He has enjoyed widespread popularity and was re-elected last year with 72 percent of the vote. He made national news as a champion of gay marriage. Newsom also made the scandal sheets in early 2007 when his campaign director resigned after learning Newsom had an affair with the campaign director's wife.

The mayor acknowledged the affair, issued a public apology, and admitted he had a drinking problem. He has since entered a treatment program.

Newsom met Siebel after his affair ended but before it hit the papers and airwaves. The Chronicle reported that she stood by him through the ordeal that followed.

The mayor, whose second term is his last by legislative mandate, proposed to Siebel while on vacation in Hawaii last December.