Mustered out following service in the occupation of Cuba, it was reorganized as the 6th Battalion of Infantry in 1901 and expanded into a regiment of the same number in 1908, but disbanded in 1914.

The regiment served in the United States Army with the occupation force in Cuba, and mustered out at Savannah, Georgia, on May 10, 1899.

[2] On June 29, 1917, the regiment was reactivated for service in the First World War when it consolidated with elements of the 3rd Missouri to create the 140th Infantry in October 1917.

In July, the 140th had its first taste of combat in the Gérardmer sector in the Vosges Mountains, where they conducted raids on German forces.

The regiment soon participated in the Meuse-Argonne offensive, the largest battle the American Expeditionary Forces waged during the war.

After five days of intense battle, they were relieved by elements of the 1st Division and were placed in the Sommedieue sector where they launched harassing attacks on the enemy positions until the Armistice of November 11, 1918, ended the war.

[2] The regiment arrived at the port of Newport News on April 18, 1919 on the USS Nansemond, and was demobilized on May 12, 1919, at Fort Riley.

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 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.