Condon is a city in, and the seat of, Gilliam County, in the U.S. state of Oregon. The population was 682 at the 2010 census. The city, with a…Condon is a city in, and the seat of, Gilliam County, in the U.S. state of Oregon. The population was 682 at the 2010 census. The city, with an historic main street along Oregon Route 19, is a farming and ranching community. The John Day River/Cottonwood Canyon State Park, the ghost town of Lonerock and the John Day Fossil Beds are all a short drive from Historic Condon.