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Pennsylvania Business Directory, Ulman, 1854-5 - Free (Don's List)
Pennsylvania Business Directory, Ulman, 1854-5 - Free (Historic Pittsburgh)
Monongahela and Youghiogheny Valleys Directory, Thurston, 1859 - Free (RootsWeb)
Delaware, New Jersey, and Pennsylvania Physicians' and Dentists' Directory, Young, 1908 - Free (Internet Archive)
Midwest Musicians' and Allied Artists' Directory, Mid-West Concert Management, 1925-6 - Free (Internet Archive)
- although this directory is primarily for the Midwest, some listings for Pennsylvania appear on page 181