Sedro-Woolley is a city in Skagit County, Washington, United States. The population was 10,540 at the 2010 census. It is included in the Mount Vernon Anacortes, Washington Metropolitan Statistical Area.Officially incorporated on December 19, 1898, Sedro-Woolley was formed from neighboring rival towns known as Sedro and Woolley in Skagit County, northwestern Washington, 25 miles (40 km) inland from the Puget Sound, 40 miles (64 km) south of the border with Canada and 65 miles (105 km) north of Seattle.