Although General Davis petitioned McClurg to join the regular army, he instead returned to S. C. Griggs &amp; Co. as a junior partner. The firm became known as Jansen, McClurg &amp; Co. in 1872 after Griggs lost his assets in the Great Chicago Fire the year before. In 1874, McClurg founded the 1st Regiment of the Illinois National Guard, leading it for three years. In 1887, McClurg became senior partner and the company was renamed A. C. McClurg &amp; Co. President Grover Cleveland named McClurg examiner at United States Military Academy. Later that year, he received an honorary Master of the Arts degree from Yale University. The A. C. McClurg &amp; Co. was destroyed in an 1899 fire, but McClurg financed its reconstruction. The new structure, designed by Holabird &amp; Roche, is now recognized as a historic place. At the time of his death, A. C. McClurg &amp; Co. was the largest book and stationery house in the West and was among the largest in the country.