[4] When the United States entered World War I in 1917, Cain enlisted in Troop D, First Mississippi Cavalry on June 29,[5] and served as a corporal and sergeant.

[6] On August 4, 1917, while in military service, Joseph Cain married Hilda Martin of Moss Point, Mississippi.

In July 1918, Cain was commissioned a second lieutenant in Field Remount Squadron 337 of the Quartermaster Corps, serving at Camp Johnston, Florida.

[9][10] Cain was a member of the House Standing Committees on Education, Railroads, Census and Apportionment, Fees and Salaries, Commerce and Shipping, and Fisheries.

[14] In 1933, he leased 16 acres (6.5 ha) of his land in the Ramsey Springs community to the Civilian Conservation Corps for use as Camp F-16 (Unit 1484), which opened on June 21, 1935.