The 140th Infantry was reconstituted in the National Guard in 1921, assigned to the 35th Division, and allotted to the state of Missouri. It was reorganized on October 1, 1921, by redesignation of the 6th Infantry, Missouri National Guard (organized March 31, 1921; Headquarters concurrently organized and federally recognized at Cape Girardeau, Missouri), made up of companies raised in southern Missouri. The regimental Headquarters was relocated about June 1923 to Caruthersville, Missouri. The regiment, or elements thereof, was called up to perform the following state duties: riot control at a railroad workers’ strike at Moberly, Macon, and Poplar Bluff, Missouri, July 31–November 23, 1922; a workers’ strike at New Madrid, Missouri, in May 1923; Mississippi River flood relief duty at Charleston, Sikeston, and Poplar Bluff, Missouri, April 16–May 12, 1927 and January 1937; St. Francis River flood relief duties in June 1928 and every spring from 1932–1933 and 1935–1938. The regiment conducted annual summer training most years at Camp Clark, Nevada, Missouri, from 1921–1939. For at least three years, 1938–1940, the regiment also trained some 81 company-grade officers of the 102nd Division at Camp Clark and Camp Ripley, Minnesota. The regimental Headquarter relocated in January 1940 to Sikeston, Missouri. The regiment was inducted into active Federal service at Sikeston on December 23, 1940, and moved to Camp Joseph T. Robinson, Arkansas, where it arrived on January 4, 1941.