After commissioning, which was one month before the Armistice with Germany ending World War I took effect, "R-19" remained on the West Coast of the United States for nine months at San Pedro, California until March 1919, and then at San Francisco, undergoing overhaul, until June 1919. On 17 June 1919 "R-19" left the United States for the Territory of Hawaii. Eight days later she reached Pearl Harbor in Hawaii and began almost 12 years of training submarine crews and testing equipment.