One Hundred and Twenty-first Regiment
(9th Cavalry) INDIANA
(3-YEARS)

After Hood's defeat at
Nashville, the regiment was in action at Franklin with
Forrest's cavalry, losing 26 in killed, wounded and captured,
and then went into camp at Gravelly Springs, Ala., until Feb.
6, 1865, when it was ordered to New Orleans.

Here it was detached, turned over its horses, and on March 25,
arrived at Vicksburg, where it was again mounted and assigned
to garrison duty in the interior of the state. It returned to
Vicksburg May 22, and was mustered out on Aug. 28, 1865.

On April 26, 1865, by the explosion on the steamer Sultana,
the regiment lost 55 men - paroled prisoners of war. Those
who escaped the disaster reached Indianapolis early in May and
were mustered out while under parole.

Source: The Union Army, vol. 3, p. 179

……

Here are a number of reports mentioning the 9th Indiana Cavalry found in the Official Records, Vol. 48:

Part 1/Ser. 101, p. 1284
Part 2/Ser. 102, pp. 491, 720, 749, 979-81, 996 & 1040

http://ebooks.library.cornell.edu/m/moawar/waro.html
http://ehistory.osu.edu/books/official-records