Guests at the wedding confirm the pair were married at the 300-acre Folded Hills Ranch in Solvang, Calif. Bullock wore a white lace dress designed by Angel Sanchez. "She looked beautiful," one guest tells PEOPLE. "She was incredibly happy."
Bullock's rep, Cheryl Maisel, also confirmed the nuptials to PEOPLE.
James arrived at the ranch Saturday behind the wheel of a giant red monster truck. Most of the 300 guests, meanwhile, were shuttled to the ceremony from hotels in Santa Barbara 45 minutes away, but they weren't told a wedding was happening until around 8 p.m., after they had arrived.
For the wedding bands, Bullock's was a vintage ring provided by jeweler Neil Lane. James's ring was made by the Miss Congeniality star herself: Bullock learned how to do metal work, and then machined it in James's bike shop. The flowers were by Cecelia Heffernan of Flower Hardware.
Invitations to the nuptials suggested a "hoedown" theme: Guests danced to bluegrass music from the band Cousin Lovers, and other tunes were provided by DJ Tony Okungbowa from The Ellen DeGeneres Show.
Bullock, who turns 41 on July 26, and James, 36, have been dating for more than a year, after meeting when she took her young godson on a tour of the Monster Garage set in Long Beach, Calif.
It's the first marriage for Bullock, who was previously linked romantically to actors Tate Donovan, Matthew McConaughey and Ryan Gosling.
James, who owns the custom-motorcycle company West Coast Choppers, has been divorced twice, most recently from adult-film actress Janine Lindemulder. But despite his born-to-be-wild past, the father of three young children comes across as "very low key, very quiet, almost shy," Miss Congeniality 2 director John Pasquin told PEOPLE in April.
Added producer Marc Lawrence: "He's similar to Sandy in that he's not looking for publicity."
Indeed, the couple have kept their romance low-profile, turning up vacationing in Hawaii, hitting a flea market in her home base of Austin and taking in a drag race near Las Vegas.
To Bullock, it's a custom-made match. Once, "I was a bolter," she told Vogue in March. "I would get so scared because my idea of marriage was not a very pleasant one. And now I look at it in a different way. I threw away what society's version of it was and I went, 'Why does it have to be anyone else's version but mine?'"