The International Salt Company series contain materials dating from 1839 to 2012 that are similar material to the location series above, but due to the large quantity of information on these topics, as well as the fact that many of these companies are or were national or even international, have warranted their own series. Each series is organized by subject, including business, correspondence, ephemera, images, publications, postcards, and films.

Researchers may also be interested in the correspondence of George M. Speaker (dates unknown) regarding Strickland vs National Salt, in the International Salt Company series. In 1901 George M. Speaker purchased preferred stock from the National Salt Company and in 1902 the company failed and was absorbed by the International Salt Company. This is the correspondence Speaker received from various stock and bond brokers and attorneys regarding the depositing of the stock and the lawsuit brought against National Salt.