Organization of the regiment:

• Company A – Centre County – Captain John I. Curtin (Governor Curtin’s half brother)
• Company B – Lancaster County – Captain Henry A. Haines
• Company C – Mifflin County – Captain William G. Biglow
• Company D – Centre County – Captain Austin Curtin
• Company E – Centre County – Captain Henry Stevens
• Company F – Wayne County and Tioga County – Captain Charles E. Parker
• Company G – Tioga County – Captain Nelson Whitney
• Company H – Tioga County – Captain Edward G. Scheffelin
• Company I – Tioga County – Captain Francis M. Hill
• Company K – Columbia, Lancaster County – Captain Ezekiel Y. Rambo

Expedition into Lower Maryland to monitor elections

Operations against James Island, S.C.,

Action on James Island

The regiment was part of a force which was attacked by Confederate forces. The 47th Georgia Infantry was forced to retreat, leaving a number of casualties. The 45th lost one man mortally wounded.

Battle of Secessionville

The regiment was commanded by Major John M. Kilbourne, but had no casualties.

Operations on the Rapidan and Rappahannock Rivers

Battle of South Mountain

The regiment fought at Fox’s Gap, commanded by Lt. Colonel Curtin while Colonel Welsh commanded the brigade. The fighting was uphill, in  rocky and heavily wooded terrain which was closely contested by the enemy. But the badly outnumbered Confederates were driven back over the summit and retreated toward Sharpsburg.

The 45th Pennsylvania lost 145 casualties. Lieutenants James Cole and George Smith were killed, Lieutenant William Grove was mortally wounded, Lt. Colonel John Curtin was lightly wounded in the arm but remained in command, and Captain Theodore Gregg was wounded.

Second Lieutenant Rees G. Richards was promoted to Captain of Company G.

Battle of Antietam

From the War Department tablet for Welsh’s Brigade at Antietam:

On the morning of the 17th Welsh’s Brigade was in reserve on the eastern slope of the ridge on the left bank of the Antietam, nearly opposite the Burnside Bridge. About 2 P.M., after Sturgis’ Division had carried the bridge, the Brigade crossed and, following the road to Sharpsburg about 250 yards, formed line west of the road.

The Brigade then advanced over the high ground west of the road, gradually crossing to the east, until its right was near this point, its center in the ravine and at the stone mill, and its left in the apple orchard beyond, when the attack of A.P. Hill on the left flank of the Corps compelled it to withdraw to the banks of the Antietam, where it remained until the evening of the 18th.

From the monument to the 45th Pennsylvania at Antietam:

The Regiment advanced 264 yards Northwest of this point, retiring to this position later in the day.

The 45th Pennsylvania Infantry Regiment lost 1 man killed, 36 men wounded and 1 man missing.

Battle of Fredericksburg

The regiment crossed the Rappahannock at the lower crossing, joining Franklin’s Grand Division, but was in reserve and suffered no casualties. On the 15th it recrossed the river and returned to its camp at Falmouth.

Burnside’s 2nd Campaign (Mud March)

Siege of Vicksburg

Captain Edward A. Kelsey of Company K was promoted to Major and First Lieutenant Andrew J. Fessler was promoted to Captain of Company K.

Siege of Jackson

Captain William Chase of Company I was wounded.

Burnside’s Campaign in East Tennessee

Blue Springs

The regiment lost 21 casualties, including Captain R. Chessman, who was wounded

Knoxville Campaign

Lenoir Station

Captain Hart of Company I with a wagon train and 16 men were captured

Campbell’s Station

Siege of Knoxville

Operations in East Tennessee

Rapidan Campaign

Battle of the Wilderness

The regiment lost 145 casualties. Lieutenant Evan R. Goodfellow was killed, Captain John Campbell of Company E was mortally wounded, and Captains William Chase and Andrew Fessler and Lieutenant Cyrus Bruner were wounded.

First Lieutenant John Beck was promoted to Captain of Company E.

Battle of Spotsylvania Court House

Lieutenant John Irvin was wounded.

Assault on the Salient

The Ninth Corps supported Hancock’s attack on the Salient with an advance and a three hour fight.

North Anna River

Totopotomoy

Battle of Cold Harbor

The regiment lost 163 casualties in three days of fighting out of 300 effectives. Lieutenants De Witt Hoig and George Scudder were killed, Major Edward A. Kelsey was mortally wounded and Lieutenants John Gelbaugh and John Rogers were wounded.

Bethesda Church

Grant’s First Assault on Petersburg

The regiment lost 3 killed and 18 wounded. Captain Chessman and Lieutenant Harvey Benner were wounded and Colonel Curtin was badly wounded in the shoulder and carried from the field.

Siege of Petersburg

Mine Explosion (Battle of the Crater)

The regiment fought in the Crater, bringing 210 men under Captain Theodore Gregg. It lost 6 killed and 22 wounded, with 39 men missing. Captain Edgar Eyde and Lieutenants Adolph Campbell and Ephraim Jeffers were wounded and Captain Rees Richards of Company G was captured.

Corporal Franklin Hogan of Company A earned the Medal of Honor for capturing the colors of the 6th Virginia Infantry.

Poplar Springs Church

The brigade was surrounded, and Lt. Colonel Theodore Gregg unsuccessfully tried to cut the regiment through to Union lines. Lieutenant James Gregg was killed, Captain Andrew Fessler of Company K was wounded and captured, and Lt. Colonel Theodore Gregg and Captains John Trout of Company C were captured along with the balance of the regiment, some 150 men.

Lieutenant Roland C. Chessman was promoted to Captain of Company F.

Peeble’s Farm

There were only 92 survivors of the regiment.

Battle of Boydton Plank Road (Hatcher’s Run)

Fort Stedman

Fall of Petersburg

Grant ordered a final grand assault all along the lines. The regiment captured Fort Hill and a six gun battery. Lieutenant Levi Robb was mortally wounded. Captains Chessman, commanding the regiment, and Lafayette Lord were wounded, with Captain Chessman losing his leg.