Brown's move frees up additional state funding and resources to help in the cleanup efforts.
"This emergency proclamation cuts red tape and helps the state quickly mobilize all available resources," Brown said. "We will do everything necessary to protect California's coastline."
The spill started out spanning about four miles Tuesday, but it has since spread to cover approximately nine miles of coastline, U.S. Coast Guard Capt. Jennifer Williams said at a news conference Wednesday.
Up to 105,000 gallons of oil spilled from an onshore pipe and approximately 21,000 gallons of oil reached the sea, according to initial estimates.
The cause of the pipeline rupture is under investigation by the Environmental Protection Agency.
Cleanup crews hit the beach at 8 a.m., scooping up the globs of oil-covered seaweed and sand. Three vessels were on the water, cleaning off the oil from the surface, and another six vessels were trying to corral the oil to keep it from spreading.
"Oil recovery tends to be a complicated process that involves a lot of manual labor and taking environmental factors like wind, currents and weather into consideration. It can be a slow process, but we want to make sure that we do it right so we can get the beaches back to its pristine condition," Williams said.
PHOTOS: Refugio State Beach oil spill
So far, 6,090 gallons of oil have been collected by vacuum trucks, skimmer boats and other resources. It remains unclear how long the cleanup will take or how much it will cost.
"Oil recovery tends to be a complicated process that involves a lot of manual labor and taking environmental factors like wind, currents and weather into consideration," Williams said. "It can be a slow process, but we want to make sure that we do it right so we can get the beach back to its pristine condition."
The oil came from a ruptured 24-inch pipeline on the north side of the 101 Freeway near Refugio State Beach, about 20 miles west of Santa Barbara. The break was discovered by a civilian who reported it to authorities around noon Tuesday.
The pipeline, which was constructed in 1987 and is owned by Santa Maria-based Plains All-American Pipeline, was shutoff about three hours later.
Plains All-American Pipeline released this statement following the spill: "Plains deeply regrets this release has occurred and is making every effort to limits its environmental impact. Our focus remains on insuring the safety of all involved."
The Coast Guard, county emergency officials and state parks officials were cleaning up the spill. Boats from the nonprofit collective Clean Seas also were providing help but were having trouble because so much of the oil was so close to the shore, Williams said.
Photos from Santa Barbara-based online news website Noozhawk showed birds caught in the muck. However, officials did not have a count on how many animals were injured or killed following the spill.
"Every effort will be made to minimize the damage to the environment, including taking care of all our wildlife," said Mark Crossland, a captain with the California Department of Fish and Wildlife. "Resources at risk include environmentally sensitive shorelines, sea birds, marine mammals and kelp beds."
Refugio State Beach is closed, as is the beach-side campground. That shutdown is expected to last through the upcoming Memorial Day weekend.
The California Department of Fish and Wildlife closed fishing and shell fish harvesting in Santa Barbara County from one mile west of Refugio State Beach to one mile east of the beach at the recommendation of the Office of Environmental Health Hazard Assessment.
The accident occurred on the same stretch of coastline as a 1969 spill that at the time was the largest ever in U.S. waters and is credited for giving rise to the American environmental movement. Several hundred thousand gallons spilled from a blowout on an oil platform and thousands of sea birds were killed along with many marine mammals.
The stretch of coastline is home to offshore oil rigs and small amounts of tar and seepage regularly show up on beaches.
The spill is the largest in years and the Santa Barbara-based Environmental Defense Center said to have it occur in "a sensitive and treasured environment is devastating to watch." The group expressed special worry for the many species of whale that migrate through the area.
The Santa Barbara County District Attorney and State Attorney General are looking into possible civil or criminal liability for the spill.
The Unified Command has established a Joint Information Center for public information located at the County Emergency Operations Center in Santa Barbara. For more information, contact the Joint Information Center at (805) 696-1188. For individuals who want to file a claim for compensation, contact officials at (866) 753-3619.
For individuals who wish to volunteer in the clean-up effort, visit calspillwatch.com for more information.
The Associated Press contributed to this report.