High Quality Content by WIKIPEDIA articles! Eureka is an unincorporated township in and the county seat of Eureka County, Nevada, United States. Eureka is by far the largest community in Eureka County. Attractions include the Eureka Opera House (built in 1880 and restored in 1993), Raine`s Market and Wildlife Museum (built 1887), the Jackson House Hotel (built 1877), and the Eureka Sentinel Museum (housed in the 1879 Eureka Sentinel Newspaper Building).