I believe the Captain Mattingly was Captain of Company G 6th West Va Infantry. Might help in finding Simpson.

Sixth Infantry
WEST VIRGINIA
(3-YEARS)

Sixth Infantry. -- Col., Nathan Wilkinson; Lieut.-Cols., John
F. Hoy, Larkin Peirpont; Majs., John B. Frothingham, John H.
Showalter, Larkin Peirpont, Edward A. Bennett.

The 6th infantry was organized by authority of the war
department and was mustered into the U. S. service from Aug.
to Dec., 1861, for the purpose of guarding the Baltimore &
Ohio railroad in the state. During the years 1862 the
companies were moved about from place to place as their
services were needed.

Cob. A and G were attacked at Weston in August by Gen. Jenkins
and compelled to retire with a loss of 6 men wounded. A part
of the regiment under command of Capt. Mattingly of Co. G --
124 officers and men -- was attacked by Col. Jackson with 700
infantry, 75 cavalry and a piece of artillery at Bulltown in
October, but the enemy was repulsed after a fight which lasted
for several hours.

In McCausland's attack on the Union forces at New Creek in
August, Cos. A, G and L were engaged, and the report says they
"behaved with conspicuous gallantry, losing 2 men killed and 4
wounded."

The non-veterans were mustered out at the expiration of the
original term of enlistment and the veterans and recruits were
retained in service until June 10, 1865, when they were
mustered out by order of the war department.

Source: The Union Army, vol. 2, p. 301

**********************************************************************************

OCTOBER 13, 1868.--Skirmish at Bulltown, W. Va.

Report of Capt. William H. Mattingly, Sixth West Virginia, Infantry.

BULLTOWN,
October 13, 1863.
SIR: We were attacked this morning at 4.30 o'clock by Col.
William L. Jackson, with about 1,000 men and two pieces of artillery.
They charged our fortifications on the northeast side. We fell back
to our main fortification. They pursued us until within a few yards
of our fortifications when we poured it into them strong and repulsed
them handsomely, with a loss of not less than 50 killed and wounded.
They then sent us a flag of true, ordering us to surrender. I told
them to come and take us. They continued fighting until 4. 30 o'clock
this evening, when they retreated. We gave them 9 of their killed,
who were in our line.

We have taken 1 lieutenant and 1 private, who are badly wounded.
We captured 2 privates, but they are not wounded. Our casualties
are myself, wounded (it is thought mortally) in the thigh, the bone
being badly broken, early in the action. You will send by all possible
dispatch a surgeon; send best that you can. Send re-enforcements
and ammunition.

Rebels withdrew in the direction of Sutton. Prisoners say they
were expecting General Jenkins to assist.

WM. H. MATTINGLY,
Captain, Commanding United States Forces.

Col. N. WILKINSON,
Brigade Commander, Clarksburg.

Source: Official Records
CHAP. XLI.] SCOUT TO INDIANTOWN, N. C. PAGE 481-48
[Series I. Vol. 29. Part I, Reports. Serial No. 48.]