Charles A. Spring Jr. (1826–1901) was a prominent Chicago capitalist during its transition from a frontier town of 30,000 in the 1850s to an industrial metropolis of more than 1.7 million at the turn of the 20th century. He was a key figure in its rise, serving as inventor Cyrus McCormick's closest adviser and as general manager of the McCormick Harvesting Company for many years.