The memorial, planned through social media, was scheduled to begin at noon, but mourners began arriving hours beforehand to leave flowers, candles, stuffed animals and other tributes.
By afternoon, about 5,000 people, including entire families with children, dropped by, Los Angeles County Sheriff's Capt. Mike Parker said, adding that the gathering was mostly peaceful. A man was arrested after deputies spotted him carrying a partially hidden and loaded gun; and 40 citations were issued for illegal parking, Parker said.
Many arrived in cars built for speed, and the sounds of engines revving echoed close to where Walker and his friend died on Nov. 30. The event concluded Sunday evening with a cruise through the area 30 miles northwest of downtown Los Angeles.
Walker, 40, was killed when the Porsche Carrera GT he was riding in smashed into a light pole and tree and then burst into flames. The actor's friend and financial adviser, Roger Rodas, who was driving, also died. Authorities say speed was a factor in the crash.
The two had bonded over a passion for fast cars. They co-owned an auto racing team named after Rodas' custom car shop, Always Evolving, and Rodas, 38, drove professionally for the team on the Pirelli World Challenge circuit this year.
On Sunday, Los Angeles County sheriff's deputies directed often-heavy traffic as mourners passed by the crash site on foot and in cars.
Many of the early arrivals parked in a nearby church lot, where they milled around and bundled up against chilly morning temperatures in the 40s.
Among those who turned out at the crash site early was Edi Maya, a gardener who worked in Walker's neighborhood and said he chatted with the actor from time to time.
"I work next to his house every week, twice a week. Seeing those candles there, it's heartbreaking," he told KABC-TV.
Actor Rick Yune, who co-starred with Walker in "The Fast and the Furious," also stopped by.
"We mourn his loss but ... we can at least remember how great a guy he was and celebrate his life," Yune told reporters.
Walker was in Santa Clarita for a fundraiser his charity, Reach Out Worldwide, organized for victims of the recent Philippines typhoon. The event took place at Rodas' shop, and the two stepped away for what was supposed to be a short drive in Rodas' car.
The limited-edition Porsche was previously owned by IndyCar driver Graham Rahal, who has said it could be difficult to drive.
Walker, the star of five of the six "Fast & Furious" movies, was the face of the franchise. He was making the seventh film in the series when he died.
Universal Pictures has shut down production while it contemplates how it might go forward without him.