D.C. Mun. Regs. tit. 10, r. 10-C220
The Board's determination whether to list a property as a historic landmark, as provided in D.C. Official Code § 6-1102(6)(B), is made when the Board votes to designate or deny designation of the property. This date is the official designation date. A historic landmark designation is final when the copy of the official designation order is mailed to the property owner. For the purposes of D.C. Official Code § 6 - 1102(6)(B), the application for designation is considered pending until the designation is final.
A historic district designation shall become effective thirty (30) days after the SHPO publishes in the D.C. Register a notice of nomination or determination to nominate the property to the National Register.
D.C. Mun. Regs. tit. 10, r. 10-C220