The Aug. 24 quake resulted in more than 280 injuries, devastated more than 100 wineries in the region and damaged at least 1,000 buildings, many of which were historic properties.
Although Brown declared a state of emergency after the temblor, a presidential declaration would unlock federal funds for the recovery effort.
In his letter to the White House on Tuesday, Brown said the economic impacts of the quake "will be extensive."
According to Brown, the California Department of Insurance estimated less than 5% of businesses and homeowners in Napa, Solano and Sonoma counties have earthquake insurance.
In Napa alone, city officials estimate damage to homes and business will be $300 million.
Napa, Solano and Sonoma counties also suffered damage to roads, bridges, water mains, and gas and power lines.
Napa Valley Vintners, which represents 500 wineries in the area, recently announced the creation of the Napa Valley Community Disaster Relief Fund and said it planned to donate $10 million toward things like replacing windows at people’s homes, counseling and temporary housing.
The Red Cross, meanwhile, continues to provide food and drinking water to more than 2,000 people in the region. And two emergency shelters remain open, housing 53 Napa and Solano County residents.
Brown noted that the powerful earthquake even damaged the control tower at Napa County Airport, prompting the use of a temporary Federal Aviation Administration tower.
"The incident is of such severity and magnitude that an effective response is beyond the capabilities of the state and affected local governments, and supplemental federal assistance is necessary," Brown wrote.