Eureka is the principal city and county seat of Humboldt County in the Redwood Empire region of California. The city is located on U.S. Route 101 on the shores of Humboldt Bay, 270 miles north of San Francisco and 100 miles south of the Oregon border. At the 2010 census, the population of the city was 27,191, and the population of Greater Eureka was 45,034.
Eureka is the largest coastal city between San Francisco and Portland, Oregon, and the westernmost city of more than 25,000 residents in the 48 contiguous states. The proximity to the sea causes the city to have an extremely maritime climate with very small annual temperature differences and seasons mainly being defined by the rainy winters and dry summers, whereas nearby inland areas are much hotter in summer. It is the regional center for government, health care, trade, and the arts on the North Coast north of the San Francisco Bay Area. Greater Eureka, one of California's major commercial fishing ports, is the location of the largest deep-water port between San Francisco and Coos Bay, a stretch of about 500 miles.