The horse was enveloped in mud and his rider was also stuck for a time. After freeing herself, she stayed by his side, trying to comfort him as they waited for help.
The incident was reported around 6 p.m. in Shadow Hills on the eastern side of the Hansen Dam recreation area.
The woman and horse were first spotted by AIR7 HD, which helped alert firefighters to their exact location.
Sherry Leigh said she normally doesn't go off regular trails when she rides Ziggy. This time they did and faced the consequences.
"He instantly sank to his belly," she told Eyewitness News. "I didn't try and make him fight or struggle to get out. I stepped off him. I was up to my knees. It was like a suction cup. I couldn't get out."
The rescue team located Leigh and Ziggy and worked to get ropes under him to try to pull him out of the mud. The rope was attached to a winch on a firefighter truck parked nearby.
The first attempt ran into trouble when the saddle snapped free of the ropes and the firefighters had to start over.
They used shovels to clear mud from around Ziggy and brought in plywood to help with footing.
The firefighters were also petting the horse in an effort to keep him calm during the rescue.
Once freeing the animal from the mud, firefighters dragged him on his side over the plywood.
Initially Ziggy was not moving its leg as he was pulled free of the mud, creating some concern for his health.
But minutes later, the animal was seen walking comfortably on his own legs. Leigh later said his only issue was an eye swollen from the mud.
Horse's rider speaks to Eyewitness News:
Leigh spoke to Eyewitness News shortly after the rescue.
"It was scary. It was scary for me. And then to see all the firefighters come together. I can't even express my gratitude to all of them for pulling together and getting him out without injury," she said.
She said she is an experienced rider and normally doesn't go off established trails. This time she did and quickly regretted it. They encountered the mud and Ziggy sank into it past his belly, she said. She tried to keep him calm and not try to kick or struggle his way out of the mud.
The horse was believed to weigh around 900 to 1,000 pounds.
A veterinarian who treated Ziggy said another horse got stuck in the area on Easter Sunday. She said similar incidents happen every year in the area.
In the same area, an 18-year-old woman was rescued from the mud and said her 21-year-old friend was missing and had last been seen several hours earlier.
Firefighters were able to locate and safely rescue the second person, a freelance photographer, several hundred yards from the site of the horse rescue.