< to June • July 1861
Commanded by Brigadier General George Cadwallader
The 1st Division was discontinued on July 25, 1861.
| 1st Brigade | Colonel George Thomas | |
| 6th Pennsylvania Infantry Regiment | Colonel James Nagle | 7/18 to Harrisburg to muster out |
| 21st Pennsylvania Infantry Regiment | Colonel John F. Ballier | 7/31 to Philadelphia to muster out |
| 23rd Pennsylvania Infantry Regiment | Colonel Charles P. Dare | 7/20 to Philadelphia to muster out |
| Philadelphia City Troop Cavalry | Captain Thomas James | |
| 2nd United States Cavalry (Cos. ACF&K) | to Dep. Shenandoah – 1st Brig. | |
| 4th U.S. Artillery (detatchment) | Captain Abner Doubleday | 1 8″ howitzer and 1 24-pounder |
| 3rd Brigade | Brig. Gen. Alpheus S. Williams | |
| 7th Pennsylvania Infantry Regiment | Colonel William I. Irwin | to Harrisburg 7/22 for muster out |
| 8th Pennsylvania Infantry Regiment | Colonel A.H. Emley | to Harrisburg 7/22 for muster out |
| 10th Pennsylvania Infantry Regiment | Colonel Sullivan A. Meredith | to Harrisburg 7/23 for muster out |
| 20th Pennsylvania Infantry Regiment | Colonel Wiliam H. Gray | to Philadelphia 7/24 for muster out |
| 4th Brigade | Col. J. C. Longenecker (until 7/2) Colonel Dixon S. Miles |
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| 9th Pennsylvania Infantry Regiment | Colonel Henry C. Longnecker | 7/21 to Harrisburg to muster out |
| 13th Pennsylvania Infantry Regiment | Colonel Thomas A. Rowley | 7/21 to Harrisburg to muster out |
| 16th Pennsylvania Infantry Regiment | Colonel Thomas A. Ziegle | 7/21 to Harrisburg to muster out |