As the end of war approached and hostilities with the Sioux Indians loomed, Raynolds's knowledge of and experiences in the Great Lakes region became more important to the army than his command of the fortifications of Harpers Ferry.
Promoted to the permanent rank of colonel on January 2, 1881, Raynolds continued serving with the Corps of Engineers supporting a variety of harbor and river navigational improvements until his retirement in 1884, after a military career that spanned 40 years [REF].