- 1 McBride, Francis Scott, 1872-1955
- 1 McCaffrey & Bro.
- 1 McCaffrey's Pennsylvania File Works
- 13 McCahan Sugar Refinery
- 1 McCallinott's Woolen Factory
- 3 McCallum Street
- 2 McCallum's Carpet Factory
- 1 McCallum's Cotton Factory
- 1 McCambridge Co. Plumbing Fixtures.
- 1 McCartersville
- 1 McCarty's Fulling Mill
- 1 McCauley Dyeing Co
- 1 McCay, J. Steam Box Factory
- 2 McClain, P.A. & Co. (hay, wagon shed, stable)
- 8 McClellan, George B. (George Brinton), 1865-1940
- 1 McCord House
- 2 McCullough American Galvanizing Works
- 1 McCullough Iron Co.
- 1 McDonough's theatre
- 1 McDowell, James, 1795 - 1851
- 2 McFerran, Armstrong & Co.
- 1 McGillicuddy, Cornelius (Connie Mack), 1862–1956
- 1 McIan, Robert Ronald, d. 1856
- 2 McIlvain, F.M. Iron Foundry
- 2 McIlvaine's Lumber Yard
- 1 McKay Sewing Machine Association
- 4 McKean Street
- 1 McKean, W. V. (William Vincent), 1820-1902
- 2 McKeesport, Pennsylvania
- 1 McKell's Mills
- 1 McKenzie Flower Garden
- 3 McKeone, Van Haagen & Co.
- 1 McKim, Mead & White, Architects
- 1 McKinley, Horn & Clement Co. Ltd. Notions (Firm)
- 1 McKinley, W.S, Drug Mill
- 1 McLanahan & Bencker, architects
- 1 McLean, Wilmer, 1814-1882
- 2 McMahon, Charles (stable, wagon shed)
- 2 McMichael, Morton, 1807-1879
- 1 McNab & Harlin Manufacturing Co.
