- 1 Maurice Fischer's Sons
- 1 Maurice H. Power (Firm)
- 3 Mauritius
- 1 Maverick, P. R. (Peter Rushton), 1755-1811
- 2 Maw & Co.
- 1 Maxentius, Marcus Aurelius Valerius, Emperor of Rome, d. 312
- 4 Maxwell, Mrs.
- 1 Maxwell's Prepared Gypsum Factory
- 1 Mayaud Bros.
- 5 Mayer's Art Institution
- 11 Mayfair, Pennsylvania
- 1 Mayland Mill Dam
- 1 Mayland's Mill
- 22 Mayors
- 1 Maypole Inn
- 1 Maypoles
- 1 Mays Landing, New Jersey
- 1 Mazzini, Giuseppe, 1805-1872
- 3 McAdoo, William Gibbs, 1863-1941
- 21 McArthur, John Jr. (1823-1890), Architect
- 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
