| Aluminum Company Of America | Lancaster | PA |
| Aluminum Company Of America | Lebanon | PA |
| Aluminum Company Of America | Glassmere | PA |
| Aluminum Company Of America | Philadelphia | PA |
| Aluminum Company Of America | Pittsburgh | PA |
| Aluminum Smelting & Refining | Philadelphia | PA |
| Amalgamated Silk | Allentown | PA |
| Amber Realty | Philadelphia | PA |
| Ambric Testing & Engineer | Philadelphia | PA |
| Ambrose Augusterfer | Hollidaysburg | PA |
| A M Byers | Ambridge | PA |
| A.M. Byers | Pittsburgh | PA |
| Amchem Products | Ambler | PA |
| Am. Department | Middletown | PA |
| Amergen Energy | Middletown | PA |
| American Asbestos | Norristown | PA |
| American Austin Car | Butler | PA |
| American Axe & Tool | Glassport | PA |
| American Axe & Tool | Beaver Falls | PA |
| American Bank Note | Philadelphia | PA |
| American Bantam Car | Butler | PA |
| American Baptist Publication Society | Philadelphia | PA |
| American Brake Shoe | Meadville | PA |
| American Brake Shoe | New Castle | PA |
| American Bridge | Philadelphia | PA |
| American Bridge | Pencoyd | PA |
| American Bridge | Clairton | PA |
| American Bridge | Northampton | PA |
| American Bridge | Economy | PA |
| American Bridge | Pittsburgh | PA |
| American Bridge | Leetsdale | PA |
| American Bridge | Ambridge | PA |
| American Bridge Shipyard | Pittsburgh | PA |
| American Can | Philadelphia | PA |
| American Can | Chambersburg | PA |
| American Can | Fairless Hills | PA |
| American Can | Morrisville | PA |
| American Can | Easton | PA |
| American Car & Foundry | Berwick | PA |
| American Car & Foundry | Milton | PA |
| American Chain & Cable | Monessen | PA |
| American Chain & Cable | Reading | PA |
| American Chain & Cable | Braddock | PA |
| American Chain & Cable | York | PA |
| American Cigar | Philadelphia | PA |
| American Clean Tile | Lansdale | PA |
| American Coke | Pittsburgh | PA |
| American Coke | Lambert | PA |
| American Cyanamid | Bridgeville | PA |
| American Dredge | Chester | PA |
