D.C. Code § 47-836
The property owned or occupied by the Washington Terminal Company, or by the Philadelphia, Baltimore and Washington Railroad Company, or by the Baltimore and Ohio Railroad Company under authority of this Act, or otherwise, together with the improvements that may be put thereon, shall be subject to taxation in the District of Columbia in the same manner and to the same extent as other property in the District, and all tracks and sidings shall be taxed as real estate; provided, that no assessment, valuation, or tax shall be made, laid, or levied on the stations, terminals, and lines of railroad located, constructed, or maintained under the authority of this act, in excess of that which would or could be lawfully made, laid, or levied if said stations, terminals, and lines of railroad were located, constructed, and maintained without the use of bridges, tunnels, viaducts, retaining walls, or other structures necessary or properly employed to elevate or to depress the same as required by this Act; it being the true intent and meaning hereof that the lines of railroad and terminals hereby authorized shall be assessed and valued for the purpose of taxation and taxed on the same basis as if the same were not constructed and maintained by means of such bridges, tunnels, viaducts, retaining walls, and other structures; provided, that such portions of the terminal structure or viaduct as may be constructed and used for storage or like commercial purpose shall be subject to taxation in the same manner as other property in the District of Columbia.
D.C. Code § 47-836