 On 17 July 1920, when the Navy adopted the modern system of alpha-numeric hull designations, she was classified as a fleet tug and redesignated AT-16.On 31 January 1936, a number of old tugs previously classified as fleet tugs were reclassified as harbor tugs, and "Tillamook" became a harbor tug designated YT-122.She received her final classification, as a medium harbor tug, on 13 April 1944 and was redesignated YTM-122.