D.C. Code § 47-1020

A certain piece of land situated in the City of Washington, District of Columbia, known as lots 9 and 11, in square 788 of the plan of that City, and occupied by the church known as Saint Mark’s Protestant Episcopal Church, and all the buildings, grounds, and property appurtenant thereto and used in connection therewith in the District of Columbia, shall be exempt from any and all taxes or assessments, national, municipal, or county.