Barry H. Landau, the once-esteemed collector of presidential memorabilia, admitted in court Tuesday to stealing thousands of documents treasured for their national and cultural significance from historical societies and libraries stretching from Baltimore up the East Coast.

Landau’s guilty plea in federal court to two criminal counts involving theft of artwork revealed a scheme in which prosecutors said he compiled lists of items to steal and matched the names of historic icons to their “potential monetary value.”

Authorities said that Landau, 63, used various means to distract librarians and staffers in four states, sometimes with cupcakes but also by using aliases. He and his assistant concealed documents in secret pockets sewn into jackets and sandpapered off identifying marks.

The FBI found 10,000 papers and “objects of cultural heritage” during searches of Landau’s apartment in New York. Court documents say that investigators traced 4,000 of the items “as being stolen from libraries and repositories throughout” America.

Federal prosecutors have described the scope of the thefts as “truly breathtaking,” with stolen documents ranging from a 15th-century manuscript from Lorenzo de Medici to three inaugural addresses delivered by Franklin D. Roosevelt in 1937, 1941 and 1945, with the former president’s handwritten notes and corrections.

Barry Landau and some of his collection of inaugural memorabilia in his Manhattan apartment. (Helayne Seidman)