Republic is a city in Ferry County, Washington, United States. The population was 992 at the 2020 census. It is the county seat of Ferry County. It was the largest mining camp in the Republic Mining District, and home to the "Hot Air Line" railway.

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.

The first ore mill for processing low grade ore in the district was constructed in May, 1898, while highest grade ores were hauled 80 mi (130 km) east to Marcus, Washington partway by cart and then via the Spokane Falls & Northern branch line for the remaining distance. Between 1899 and 1900, stamp mills were constructed at the Mountain Lion mine in the northwest part of camp and the Republic Mine in the south resulting in a brief period where all of the district's ore was milled in the camp. The Mountain Lion Gold Mining company 100-ton mill used a combination of mercury plate amalgamation followed by MacArthur-Forrest cyanide leaching. However, because of much lower gold and silver recovery rates, combined with the soon to arrive rail lines, the mill was soon shut down. The 200-ton Republic mill processed the ore by first roasting the finely crushed ore, followed by cyanide leaching, with the first loads of ore being processed in October 1900.

In July 1901, the Republic mine and mill both shut down because of the milling cost, and a lack of enough profitable ore being recovered. Ores in the Republic District were noted to have increasing percentages of silver concentration in the lower portions of the ore bodies, and the Republic mill did not provide more than a 50% return on assayed ore value, dooming the mill. The Republic mine remained inactive until 1902 when the arrival of railroads in the town made mining profitable again. From 1902 to 1909, ore was freighted north to British Columbia and then west to smelters on the coast for processing, with periods where shipments up to 1,000 st (6,400 kg) of ore a week were regular.

The Republic mining District encompassing Republic and the surrounding areas, had no defined borders as of 1909 when the geologist Joseph B. Umpleby visited, but included six townships with a center "a little west of the south end of Curlew Lake". At the time of the visit Republic was the most important mining camp in the county and the largest with a population of around 1,500.

In July 1897, Philip Creasor built a two-story hotel at the townsite, originally called Eureka. 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. Two separate rail lines granted access to the area, Great Northern Railways Spokane Falls & Northern branch line and the locally owned Republic and Kettle Valley Railway, commonly called the "Hot air line" from Grand Forks, British Columbia. During the summer of 1900, Swedish immigrant Charles E. Anderson first opened Anderson's Grocery.

The Spokane and British Columbia Railway, originally the Republic and Kettle Valley Railway, was a short lived standard-gauge private rail company based out of Republic operating between Republic, Grand Forks and Lynch Creek British Columbia. The line was locally known as the "Hot Air line". The line began operation in 1902 as the Republic and Kettle Valley Railway, before being bought out in 1916. The company was initially incorporated in 1901 with J. Stratton as president, with construction of the line between Republic and Danville, Washington at the United States-Canadian border being contracted to the Republic and Grand Forks Construction Company, itself owned by Stratton. The rail line paralleled the Great Northern spur line from Republic through Malo and Curlew, Washington to Danville. The northern line was initially surveyed by the Republic and Kettle River company, but they were forced to build on higher ground beyond the Great Northern land boundaries. On January 2, 1902, the railroad was also approved by the Secretary of the Interior to conduct surveying for a southern line though the Colville Indian Reservation along the Sanpoil River.

During the early 1900s, Republic was home to a regional baseball team which traveled the northeast region playing other city teams such as those from Colville and Orient, Washington, plus Grand Forks, British Columbia. The city also had a brass band which would play at events such as Fourth of July celebrations which it would host with the baseball club. The Kettle River Journal of Orient reported August 1913 that the Republic Theater had been purchased by a new owner who renovated and remodeled it.