Archives hold collections of personal and institutional papers. Descriptions of the collections are often available online in documents called Finding Aids. These outline the contents of the collection, but don't necessarily include digital versions of the contents. These databases will help you find if and where personal and institutional papers are held.
Many archives include entries for their Finding Aids in Worldcat (limit your search to Archival Materials). The University Library subscribes to many databases described as archives, which will put you in touch with primary sources. These resources generally include a single publication (e.g., Vogue Magazine) or have a particular subject focus (e.g., Archive of Americana). The following list is just a sampling. To find more go to Library Search and enter Archive as your search.
Shoah Foundation Visual History Archive
Listed here are specialized libraries, architectural collections, and online resources related to your projects.
Chicago
Art Institute of Chicago Archival Collections
Detroit
Bentley Historical Library (University of Michigan)
Detroit Historical Society (see also the Historical Society's, Encyclopedia of Detroit)
Detroit Public Library Burton Historical Collection
Walter P. Reuther Library of Labor and Urban Affairs, Wayne State Univ.
Hong Kong
Foreign Architect Hong Kong Contemporary Architecture Guide (travel focus, but puts one in touch with sources)
London
RIBA (Royal Institute of British Architects) Library & Collections
National Archives - Finding Architectural Records
Los Angeles
Online Archive of California (includes university and museum archives)
Getty Center. Architecture and Design Collections
New York City
Museum of the City of New York
World Trade Center (historic buildings in Lower Manhattan)
New York Public Library Archives & Manuscripts
New York Public Library Digital Collections
Sydney
New South Wales State Archives & Records
New South Wales Archives: Colonial (Government) Architect Guide
National Archives of Australia
Directories & Guides
e-architect postings about world buildings, organized by city (online resource for contemporary architecture)
e-architect postings about world buildings, organized by country
ArchDaily Contemporary Architecture City Guides
Archives Hub, a directory of over 300 archives in the U.K.