They gathered at Manhattan Beach to take part in the sold-out Operation Jack Marathon, which serves to benefit autism-related charities, primarily Train 4 Autism, as well as other worthy causes.
The marathon, intended to be a one-time event until it surged in popularity, was created by the parents of Jack, a boy with autism.
"We wanted our son Jack to leave a legacy behind," said Jack's mother, Tiffany Felsenfeld. "We want everyone in the world to know more and more about autism."
With Jack on their mind, each runner hoped each step would bring them closer to raising awareness and money for a good cause.
"This was hard today, but it's a piece of cake compared to what Jack has to go through every day and all the other children and adults with autism," Felsenfeld said.