Source: November 1916 War Diary. Promoted from Sergeant to Lieutenant.
Find-A-Grave
Family Search: When Chauncey John Jackson was born in March 1893, in Clarinda, Page, Iowa, United States, his father, Will ‘Willie’ H Jackson, was 33 and his mother, Laura Alice ‘Dot’ Wilson, was 33. He married Dorothy May Proctor on 22 January 1916, in London, England, United Kingdom. He lived in Prairie City, Jasper, Iowa, United States in 1920 and Des Moines, Polk, Iowa, United States in 1920. He registered for military service in 1914. In 1914, at the age of 21, his occupation is listed as electrician, telephone linesman in Michigan, United States.
Born U.S.A.
Attestation paper claims he served with Pancho Villas in the “1st Battalion.”
Promoted in the field to lieutenant and then Acting/Captain.
History of the 18th Battalion CEF, "The Fighting Eighteenth" 