I can start off with the Maryland Genealogical Society. The Maryland Genealogical Society was established quite recently in 1959. The Society works in partnership with the Maryland Historical Society, the state's oldest continuously operating cultural institution.
Here is a description of the Maryland Historical Society from their website:
Founded in 1844, the Maryland Historical Society (MdHS) is the state’s oldest continuously operating cultural institution. In keeping with the founders’ commitment to preserve the remnants of Maryland’s past, MdHS remains the premier institution for state history. With over 350,000 objects and seven million books and documents, this institution now serves upward of 100,000 people through its museum, library, press, and educational programs.I will also focus on the historical and genealogical resources in Washington, D.C.