National Liberty Memorial Act - Authorizes the National Mall Liberty Fund D.C. (previously, the Black Revolutionary War Patriots Foundation) to establish a memorial on specified federal land in the District of Columbia to honor the slaves and free persons who served as soldiers and sailors or provided civilian assistance during the American Revolution and to honor the men, women, and children who ran away from slavery or filed petitions with courts and legislatures seeking their freedom. Requires the National Mall Liberty Fund D.C. to establish the memorial.