Republic was founded by gold prospectors in the late 19th century. Mining claims were first made along Eureka Creek on March 1, 1896, after the northern half of the Colville Indian Reservation was vacated on February 21. On March 5, 1896, the Republic claim was staked by Thomas Ryan and Philip Creasor along Granite Creek, another branch of the Sanpoil River. The resulting Republic Mine eventually became the highest producer of gold in the county. On April 18, 1896, the Republic Mining District, originally called the Eureka Mining District, was established.
This town site was platted on April 29, 1898, and the post office name changed to Republic, since there was already a post office named Eureka in the state of Washington. On May 8, 1900, a special election was held which approved incorporation of Republic, and J.J. Sullivan was elected mayor. The town was then officially incorporated on May 22, 1900, and had a population of about 1800.