Additional bus companies, listed as existing during 1930's, are mentioned in the WPA American Guide Series of state guidebooks.
Suburban and interurban bus companies listed in the Russell's Official National Motor Coach Guide, which was primarily a resource for intercity bus lines.
McMahon Transportation Co. (to Manchester and Hanover PA, until 1954)
Baltimore & Annapolis Railroad Co. - replaced interurban railway, connected Baltimore with Annapolis.
Baltimore-Henryton Bus Line - suburban based in Catonsville.
Dependable Motor Tours - served Baltiimore, Oak Grove, Poplar, White Marsh, Loreley, Bradshaw, Toppa, Edgewood.
Diggs Motor Coach Co. - served Baltimore.
Harford Motor Coach Co. - no further information.
Lake Shore Bus Co. - served Baltimore, Brooklyn, Glen Burnie, Gibson Island.
Rosedale Passenger Lines - served Baltimore and suburbs.
West Shore Transit Lines - served Baltimore and St. Leonard and Solomons Island, also existed in 1930's.
Wheeler Transportation Co. - suburban served Baltimore, Middle River, Essex.
Woodstock Bus Line - suburban served Baltimore, Woodstock.
According to various issues of the magazine "Motor Coach Age", the remaining suburban bus companies acquired by the Maryland Mass Transit Administration in 1973 were Baltimore & Annapolis Railroad Co., Dundalk Bus Line, Ruxton Bus Co., and McMahon Transportation Co.