Winslow was born December 27, 1876, in Damariscotta, Maine, studied at the Art Institute of Chicago and at the École des Beaux-Arts, and joined the office of Bertram Goodhue in time for the planning of the 1915 San Diego Panama–California Exposition.
Winslow is the one credited for choosing the Spanish Colonial style for that project, a choice with a vernacular regional precedent.
[1] He moved to Southern California in 1917, where he completed the Los Angeles Public Library after Goodhue's death in 1924 and also pursued his own commissions, including a number of Episcopal churches.
With Clarence Stein, he wrote The architecture and the gardens of the San Diego Exposition.
His son, Carleton Winslow, Jr. (1919–1983), was also an architect, specializing in churches in Southern California, as well as an architectural history professor and author.