Nearly half a million people are expected to pack the event.
Booths, vendors and activity stations will cover an 8.5-mile stretch of beach, giving spectators a variety of things to do on top of watching top surfers compete in the world's largest surfing contest.
Bands Dead Country and Jimmy Eat World were scheduled to perform Friday, and a fashion show with celebrity appearances was also on the schedule.
Professional surfer Nate Yeomans spoke to Eyewitness News about his journey to the U.S. Open of Surfing.
"As an amateur, I just kind of went out there and hoped things went my way," said Yeomans. He said he was coached a few years ago by former world surfing champion Ian Carins, who taught him how to watch the ocean to read the tides.
Seventeen-year-old surfer Malia Manuel tested the waters Friday morning while warming up and said the conditions were nice and not as windy as before. Manuel won the U.S. Open of Surfing in 2008 at the age of 14.
In addition to the U.S. Open of Surfing, skateboarding competition Coastal Carnage is also slated to take place in Huntington Beach.
People from all over the country are in town for the event, and that means plenty of business for local shops and restaurants, including Michele's Sugar Shack Café. The Main Street diner was busy around the clock Friday.
"We only can handle so much business, you know? It's epic. The business - it goes off the whole week," said restaurant employee Timmy Turner.
Finding a table at the Sugar Shack may be difficult, but it's no comparison to finding a parking spot.
"Parking is tough. I know from down here being a longtime business and local. From Sixth Street anywhere up to Goldenwest is free parking, but it becomes very difficult unless you get here, gosh, 6 o'clock in the morning," said Huntington Beach resident Mike Sardette.
Many people, including Huntington Beach resident Maddy Benner, had to do just that. Benner said she had no problem pulling into a parking spot when she arrived at about 7 a.m.
"If you come down here later, you've definitely got to wait and circle around," Benner said.
Parking lots were full by 8 a.m., but Benner said she had some motivation to beat the crowds and get to the beach early.
"There's a lot of cute surfers, so that's always good," Benner said.
Admission for the U.S. Open is free. The event runs through Sunday with the finals kicking off Saturday.