There are 5 US Post Offices in Blaine County serving a total of 21,120 residents equating to 4,224 residents per post office. It's estimated that approximately 33,710 packages are handled across the 5 county post offices annually. Blaine County is a county located in the U.S. state of Idaho. As of the 2010 census, the population was 21,376. The county seat and largest city is Hailey. Blaine County was created by the state legislature on March 5, 1895, by combining Alturas and Logan counties. Its present boundaries were set on February 8, 1917, when a western portion became Camas County. The county is named after former congressman and 1884 Republican presidential nominee James G. Blaine (1830\u201393). Blaine County is included in the Hailey, ID Micropolitan Statistical Area. It is home to the Sun Valley ski resort, adjacent to Ketchum."