Costco managers on site said the store is bringing in more than 380 new jobs to the area.
"It was definitely worth the wait," Michelle Taylor, an Oakland resident said.
People started lining up in the dark overnight, hours before the ribbon was cut.
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Many, hoping to score some hard-to-find, luxury items like Pappy Van Winkle bourbon.
"We were looking for maybe some of the high-end whiskey, maybe buy them as Christmas gifts for some of our friends but they're all sold out," Miguel Carrillo, a Walnut Creek resident said.
"They have a lot of alcohol, let's just start there, we didn't buy alcohol, but they have a lot, the line was around the corner," Taylor said.
The parking lot, also full, backing up traffic in both directions of the entrance.
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"For the first time, I said it doesn't matter how long it takes to park, I am going to go into the store on the first day," Suresh Roy, a Dublin resident said.
Roy waited 15 minutes just to park, but that didn't dampen his excitement.
"I hope my cart will be full of stuff when I walk out of this place," he said.
Instead of driving to Livermore or Danville for his warehouse deals, now, he's got a much closer option.
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"So excited!" he said. "I mean, we have been waiting for this for such a long time because all the time we have to drive on both sides, it's 10 miles each way and wow, what a relief. This is a blessing to us and Costco? I love Costco!"
And other shoppers like Kellie Simms, drove in from Oakland, leaving with a cart full of the Thanksgiving essentials.
"I would come to this one more than I would closer to my house," Simms said. "Come and get your last minute items because everyone is here."
The store will be open until 8:30 p.m. on Wednesday for those still needing some last-minute Thanksgiving items.
It will close for Thanksgiving and reopen on Black Friday at 9 a.m.