Moro is a city in Sherman County, Oregon, United States. The population was 324 at the 2010 census. It is the county seat of Sherman County…Moro is a city in Sherman County, Oregon, United States. The population was 324 at the 2010 census. It is the county seat of Sherman County. It’s currently the least-populous county seat in Oregon. Moro was incorporated on February 17, 1899, by the Oregon Legislative Assembly. It was named for Moro, Illinois.