You can procure William’s 21 card file through a service provided by these boards, see:

http://history-sites.com/research/

This would include his pension file, however, I could not locate one on the Fold.3 site.

William R. Carroll

Residence was not listed; 45 years old.
Enlisted on 10/22/1863 at Dardanelle, AR as a Private.
On 10/22/1863 he mustered into "C" Co. AR 4th Cavalry
He deserted on 3/3/1865 at Dardanelle, AR
Intra Regimental Company Transfers:
* from company C to company E
(Applied for a pension in 1880)

……….

Jacob T. Harkey

Residence was not listed; 25 years old.
Enlisted on 2/27/1864 at Dardanelle, AR as a Private.
On 2/27/1864 he mustered into "C" Co. AR 4th Cavalry
He was discharged (date not stated)
Intra Regimental Company Transfers:
* from company C to company E
Other Information:
born in Pope County, AR
(Applied for a pension in 1895)

……..

Eli Harkey

Residence was not listed; 45 years old.
Enlisted on 10/28/1863 at Conway County, AR as a Private.
On 10/28/1863 he mustered into "H" Co. AR 3rd Cavalry
He died on 11/4/1864 at Little Rock, AR
Other Information:
born in Cabarrus County, NC
Buried: National Cemetery, Little Rock, AR
(His widow applied for a pension in 1865)

……

Jacob Simeon Harkey

Residence was not listed; 29 years old.
Enlisted on 10/28/1863 at Conway County, AR as a Corporal.
On 10/28/1863 he mustered into "H" Co. AR 3rd Cavalry
He was discharged (date not stated)
Other Information:
born in Cabarrus County, NC
(Applied for a pension in 1886)

……

Jefferson John Harkey

Residence was not listed; 19 years old.
Enlisted on 11/10/1863 at Conway County, AR as a Private.
On 11/10/1863 he mustered into "A" Co. AR 3rd Cavalry
He was discharged (date not stated)
Other Information:
born in Pope County, AR
died 5/26/1915 in Hopkins, TX
(Applied for a pension in 1890)

…..

John M. Harkey

Residence was not listed; 21 years old.
Enlisted on 2/23/1864 at Lewisburg, AR as a 2nd Lieutenant.
On 2/23/1864 he was commissioned into "H" Co. AR 3rd Cavalry
He was Mustered Out on 6/30/1865
(Applied for a pension in 1891)

……

Martin M. Harkey

Residence was not listed; 18 years old.
Enlisted on 10/28/1863 at Conway County, AR as a Private.
On 10/28/1863 he mustered into "H" Co. AR 3rd Cavalry
He died on 3/17/1864 at Little Rock, AR
Other Information:
born in Cabarrus County, NC

……

William J. Harkey

Residence was not listed; 27 years old.
Enlisted on 11/8/1863 at Galla Rock, AR as a Private.
On 11/8/1863 he mustered into "A" Co. AR 3rd Cavalry
He died on 7/7/1864 at Little Rock, AR
Other Information:
born in Pope County, AR
Buried: National Cemetery, Little Rock, AR
(His widow applied for a pension in 1866)

Sources used by Historical Data Systems, Inc.:
- Index to Compiled Military Service Records
- 4th Arkansas Union Cavalry - Arkansas Research

……………………………………………………………………………………….

William R. Carroll, age 45, Private, Company C, 4th Regiment Arkansas Cavalry, joined for duty and enrolled October 22,1863 at Dardanell, Ark. for 3 years, furnished horse and horse equipment, appointed Quarter Master Sergeant March 2, 1864, absent sick at home in Yell County, May 16,* reduced to the ranks June 21, 1864, still absent March 30, 1865, declared a deserter, charges removed and honorably discharged October 29, 1874 to date from March 30, 1864

* Was sick at time of attack on Dardanells May 16, 1864 and left there sick on evacuation of the place by the U. S. Troops.

Note, his record consists of 21 cards

M399: Compiled Service Records of Volunteer Union Soldiers Who Served in Organizations from the State of Arkansas