Eureka is a city on California’s North Coast and the county seat of Humboldt County. It sits on U.S. Route 101 along the shores of Humboldt Bay, roughly midway up the state’s coast between San Francisco to the south and the Oregon border to the north. The 2020 census recorded a city population of 26,512, with the wider Eureka area at 48,119.
The city is the largest coastal community between San Francisco and Portland, Oregon, and serves as the regional hub for government, health care, trade, and the arts north of the San Francisco Bay Area. Greater Eureka is a major commercial fishing port and home to the largest deep-water port between San Francisco and Coos Bay. Its economy was historically built on timber, fishing, and supplying inland gold-mining operations; today tourism, timber, health care, and services dominate, and the area is also known for cannabis as part of the Emerald Triangle.
The entire city is designated a California state historic landmark (marker #477), and it retains a well-preserved 19th-century Victorian commercial core known as the Old Town Historic District, including the Carson Mansion.
Relevance to the Zodiac case
Within Zodiac research, Eureka is noted as the postmark/origin associated with the 1990 Eureka Christmas card, one of the Letters of suspicious authorship examined in the case. This Wikipedia article on the city itself does not address the Zodiac matter; it establishes the geographic and civic facts about the place.