Additional bus companies, listed as existing during additional years or decades, are mentioned in old City Directories, and in the WPA American Guide Series of state guidebooks.
California Bus Lines - existed in 1930's.
Furse Stage Lines - served suburban Seattle, existed in 1950's to 1960's.
Independent Stages - existed in 1930's, also served Everett.
Olympic Peninsula Motor Coach Co. - existed in 1920's to 1930's.
Puyallup-Sumner Stages - existed in 1930's.