Baltimore & Washington Transit Co. - incorporated 1894, opened 1897. Operated between Takoma Park and Wildwood. Closed 1907 and electrification removed. Reopened 1910 using gasoline cars, replaced 1911 with battery cars, closed again 1913. Re-electrified and reopened 1914 by Washington & Maryland Railway Co. Leased 1918 by Capital Traction, abandoned 1937.
East Washington Heights Traction Co - incorporated 1898, opened 1895 on Pennsylvania Av., crossing Anacostia River. Converted to buses in 1923.
Kensington Railway - incorporated 1894 as Chevy Chase Lake & Kensington Railway, opened 1895, acquired in 1902 by Kensington Railway. Leased 1923 to 1933 by Capital Traction, abandoned 1935.
Maryland & Washington Railway - incorporated 1892, opened 1899. Extension within Maryland of Columbia & Maryland Railway, operated to Laurel. Acquired 1899 by City & Suburban Railway Co.
Tenallytown & Rockville Railroad - incorporated 1890, opened 1890. Extension within Maryland of Georgetown & Tenallytown Railway Co. line, operated to Rockville. Acquired 1897 by Washington & Rockville Railroad, acquired 1902 by Washington Railway & Electric Co. Converted to buses in 1935.
Glen Echo Railroad - incorporated 1889, opened 1891. Connected with Tenallytown & Rockville Railroad, operated west to Glen Echo and Cabin John. Renamed in 1896 to Washington & Glen Echo Railroad, abandoned 1900.
Washington & Great Falls Electric Railway Co. - incorporated 1892, opened 1895. Operated west to Cabin John. Acquired 1902 by Washington Railway & Electric Co.
Washington & Great Falls Railway & Power Co. - incorporated 1912, opened 1913. Connected with Tenallytown & Rockville Railroad, operated between Bethesda and Great Falls. Abandoned 1921.
Washington Spa Spring & Gretna Railroad Co. - incorporated 1905, opened 1910 within Bladensburg. Extended 1912 to Berwyn using battery cars. Renamed 1912 to Washington Interurban Railroad Co., owned by Washington Railway & Electric Co. Converted to buses in 1923.
Washington Woodside & Forest Glen Railway & Power Co. - incorporated 1895. Extension within Maryland of Brightwood Railway Co., operated to Forest Glen. Acquired 1902 by Washington Railway & Electric Co. Converted to buses in 1924.
Washington Marlboro & Annapolis Motor Lines, Inc. - service began in 1922 southeast of Washington DC via Pennsylvania Avenue by Bradbury Heights Bus Line, acquired in 1926 by Washington Marlboro & Annapolis Motor Lines. Acquired by Washington Metropolitan Area Transit Authority in 1973. Routes had been identified by letter, most routes redesignated by WMATA by adding number 12 to letter.