During the remainder of their three months service, the regiment was separated. A detachment of five companies served with Major General George B. McClellan in the Rich Mountain campaign. Another detachment was with Col. Erastus B. Tyler in a campaign against Confederate Brigadier General Henry A. Wise, who at that time had attempted an invasion of western Virginia. The remainder of the regiment guarded the Baltimore and Ohio Railroad. On August 19, they returned to Wheeling where the 3-months regiment was mustered out of Federal service on August 27, 1861.