Galvanized Yankees

Galvanized Yankees was a term from the American Civil War used to
refer to former Confederate prisoners of war who had sworn allegiance
to the Union. Due to doubts about their ultimate loyalty, Galvanized
Yankees were generally assigned to garrison forts far from the Civil
War battlefields or in action against American Indians in the west.

Regiments made up of "Galvanized Yankees"

1st U.S. Volunteer Infantry
Organized at Point Lookout, Md., January 21 to April 22, 1864. Moved
to Norfolk, Va., and provost duty there and at Portsmouth, Va.,
District of Eastern Virginia, Dept. of Virginia and North Carolina, to
August, 1864. Ordered to Milwaukee, Wis., thence to St. Louis, Mo.,
arriving there August 22. (4 Cos. remained in Wisconsin till
September, then ordered to Minnesota.) Six Companies moved from St.
Louis to Fort Rice, Dakota Territory, arriving there October 17, and
garrison duty there; at Fort Berthold and at Fort Union, mouth of the
Yellowstone, till October, 1865. Moved to St. Louis, Mo., and mustered
out November 27, 1865. Four Companies on duty in District of Minnesota
till May, 1866. Mustered out May 21, 1866.

Information taken from Dyer's Compendium