"On This Date in Cryptologic History" Calendar
1931: US Coast Guard Established Cryptanalytic Section

1 July 1931: At the urging of Elizebeth Friedman, the US Coast Guard established a seven man cryptanalytic section.
Learn more in the NSA Center for Cryptologic History's document - "Listening to the Rumrunners: Radio Intelligence during Prohibition" by David P. Mowry, as well as Elizebeth Friedman's Hall of Honor page. See links below.