D.C. Code § 47-1040
Certain property in the District of Columbia, known in the 1600's and 1700's as Cerne Abbey Manor; later the property of members of the distinguished Carroll and Sewall families, still later the office and residence of Albert Gallatin, Secretary of the Treasury, 1801-1813, who here directed the financing of the Louisiana Purchase; since 1929 the headquarters of the National Woman's Party and known as the Alva Belmont House, described as lots nos. 863, 864, and 885 in square no. 725, together with improvements thereon and outbuildings, and the furniture, furnishings, and other personal property therein, owned by the National Woman's Party, Inc., a nonprofit corporation organized and existing under the laws of the District of Columbia; shall be exempt from taxation, in recognition of the patriotic efforts made by the National Woman's Party, Inc., to preserve this historic monument, so long as the same property is owned by said National Woman's Party, Inc., and is not used for commercial purposes or for the purpose of securing a rent or income, subject to the proviso that said corporation shall maintain the said property as historical buildings which shall be preserved for their architectural, historical, and educational significance, which buildings shall be accessible to members of the general public without charge or payment of a fee of any kind at such reasonable hours and under such regulations as may from time to time be prescribed by said corporation, subject to the provisions of §§ 47-1005, 47-1007, and 47-1009.
D.C. Code § 47-1040