Lyman is a town in Skagit County, Washington, United States. The population was 423 at the 2020 census. It is included in the Mount Vernon-Anacortes, Washington Metropolitan Statistical Area. Prior to American settlement, the Chobaabish band of the Skagit people had two winter houses around what is now Lyman. One winter longhouse was locateā¦Lyman is a town in Skagit County, Washington, United States. The population was 423 at the 2020 census. It is included in the Mount Vernon-Anacortes, Washington Metropolitan Statistical Area. Prior to American settlement, the Chobaabish band of the Skagit people had two winter houses around what is now Lyman. One winter longhouse was located close to the present town, along Lyman Slough. Another winter longhouse was located across the Skagit River, at the mouth of Day Creek.