Old Chicago and North Western Terminal ca. 1912, soon after its completion
Charles Sumner Frost (May 31, 1856 – December 11, 1931) was an American architect. He is best known as the architect of Navy Pier and for designing over 100 buildings for the Chicago and North Western Railway.
Born in Lewiston, Maine, Frost was first a draftsman in Boston, and a graduate of the Massachusetts Institute of Technology. While working in Boston he worked for the firm of Peabody and Stearns. He moved to Chicago in 1882. There he began a partnership with Henry Ives Cobb. Together, they established the firm Cobb and Frost, which was active from 1882 to 1898. After the partnership ended, he worked alone. On January 1, 1898, he partnered with Alfred Hoyt Granger to form the firm of Frost and Granger. Frost and Granger were known for their designs of train stations and terminals, including the now-demolished Chicago and North Western Terminal. Frost designed 127 buildings for the Chicago and North Western Railroad alone. After Frost and Granger dissolved, Frost continued to work independently, designing such structures as the Navy Pier Auditorium.  He retired on December 31, 1928 and died on December 11, 1931 in Chicago.