• They were holding companies for major railroads.
• Their names directly indicate their rail holdings.
• Railroad collectors are likely to look in this database for certificates.

If railroad companies are true subsidiaries of holding companies, then they have separate operating management and a modicum of autonomy. Like the utility company argument above, I believe that if railroading is (or was) not important enough to be reflected in corporate names, then there is no point for me to waste my time cataloging them.

Holding companies that clearly meet requirements for inclusion include the Southern Pacific Company, the Pennsylvania Company, the Reading Company, the Canadian Pacific Ltd, and the Union Pacific Corporation.