3rd Missouri, US Reserve Corps Infantry (Three Years Service)

Members of the 3rd Missouri U.S. Reserve Corp Infantry (3 Months Service) who chose to reenlist in September 1861, when their unit was mustered out of service, were reorganized as the 3rd U.S.R.C. Infantry (3 Years Service) under the command of Colonel Charles A. Fritz, who had been the original regiment's Lieutenant Colonel.

In January 1862, the 3rd U.S.R.C Infantry (Three Years Service) was consolidated with the Gasconade Battalion to form the 4th Missouri Volunteer Infantry.