Amy, The Heinz Architectural Center is indeed located in Pittsburgh PA.  It is
part of the Carnegie Museum of Art, housed at the Carngie Museums in Oakland.
It opened a couple of years ago.  Has FL Wright's California field office
(permanent) and lots of temporary exhibits.  Just finished was "A Century of
Women Landscape Architects and Gardeners in Pittsburgh", "Selections from the
Permanent Collection".  The collection focus is on American building designs of
the 19th and 20th century.  Dennis McFadden is curator of the Center.  Need
more info?  Feel free to email me:-) Lenore Adler (CMNH Education)