On 23rd January 1920, Mount Vernon (ex-Kronprinzessin Cecilie) sailed from San Francisco for Vladivostok, via the Panama Canal, to collect 4,000 refugees, mainly Czechoslovakian troops, escaping from the civil war still raging in Russia. Some 7,000 tons of coal were loaded for the trip to Siberia. On arrival, 261 First Class passengers and 3,074 escaping troops were taken aboard, and she sailed on 13th April. Stopping at San Francisco, she collected a further 700 prisoners of war, and on 12th June arrived at Norfolk, where all the passengers were debarked.
Mount Vernon then returned to Mare Island in California, where she was laid up. Following the outbreak of the Great War, the German express liner Kronprinzessin Cecilie had been seized by US authorities on 6th April 1917 and allocated to the US Navy. She was converted into a troopship, to accommodate 3,000 troops, and six 5-inch guns were mounted for defensive purposes. She was commissioned on 28th July 1917 as USS Mount Vernon, ID-4508, and after her trials and a shake-down cruise, on 13th October she joined the New York Division of the Atlantic Fleet Cruiser and Transport Force. After sterling service in 1917 and 1918, she was decommissioned on 29th September 1919. Later laid up in Chesapeake Bay, she was eventually scrapped Baltimore in September 1940.