The Eureka Classis was part of the Reformed Church in the United States (RCUS). It existed from 1910-1985. From 1940 until in 1985 the Eureka Classis served as the continuing RCUS as the rest of the denomination had merged into the new denomination, the Evangelical and Reformed Church. On May 6, 1986 the Eureka Classis was called to order and immediately dissolved to form the Synod of the Reformed Church in the United States.