A more comprehensive directory of museums, organized by location, can be found at the Mother of All History Links website.
New Jersey State Museum, Trenton
Whitney Museum of American Art
The Frick Collection & Frick Art Reference Library
Philadelphia
Institute of Contemporary Art (ICA)
Pennsylvania Academy of Fine Arts
Univ. of Penn Museum of Archaeology & Anthropology
Pennsylvania, General
The Carnegie Museums (Pittsburgh)
The Andy Warhol Museum (Pittsburgh)
Winterthur Museum, Garden & Library (Winterthur, PA)