Crerar moved in 1862 to Chicago, where he directed a railway equipment manufacturing plant. A member of the Pullman Palace Car Company when it was incorporated in 1867, he was also a bank and railroad director.

While Crerar's library bequest did not provide for a purely science library, he expressly wished that certain novels and other works that he felt undermined morals be excluded. The library, now affiliated with the University of Chicago, contains approximately 1,000,000 volumes on physical, natural, and medical sciences as well as other subjects. Crerar's will also provided for a statue of Abraham Lincoln, resulting in a celebrated work by Augustus Saint-Gaudens in Lincoln Park, Chicago.