Below is a list of all the Union units that were in Stafford during the First Federal Occupation.

• Major General Irvin McDowell commanded the Department of the Rappahannock.
  • Brig. Gen. Rufus King’s Division:
  • Brig. Gen. C. C. Augur’s (1st) Brigade: 22nd, 24th, 30th, 84th New York Infantry and 2nd U.S. Sharpshooters
  • Brig. Gen. Marsena R. Patrick’s (2nd) Brigade: 21st, 23rd, 35th, 80th New York Infantry
  • Brig. Gen. John Gibbon’s Brigade: 19th Indiana and 2nd, 6th, 7th Wisconsin Infantry
  • Cavalry: 2nd New York (Harris Light) (8 companies)  Div. Artillery: (4 batteries)
• Brig. Gen. G. A. McCall’s Division:
  • Brig. Gen. John F. Reynolds’ (1st) Brigade  Div. Artillery: (4 batteries)
  • Brig. Gen. G. G. Meade’s (2nd) Brigade
  • Brig. Gen. Truman Seymour’s (3rd) Brigade
• Brig. Gen. E. O. C. Ord’s Division:
  • Brig. Gen. James B. Ricketts’ (1st) Brigade  Div. Artillery: (4 batteries)
  • Brig. Gen. Abram Duryea’s (2nd) Brigade
  • Brig. Gen. G. L. Hartsuff’s (3rd) Brigade
  • Cavalry: 1st Maine and 1st Rhode Island
• Maj. Gen. James Shields’ Division:
  • Brig. Gen. Nathan Kimball’s (1st) Brigade  Div. Artillery: (5 batteries)
  • Brig. Gen. Orris S. Ferry’s (2nd) Brigade
  • Brig. Gen. Erastur B. Tyler’s (3rd) Brigade
• Separate Brigades:
  • Brig. Gen. Abner Doubleday’s Brigade
  • Brig. Gen. John Geary’s Brigade (mixed infantry, cavalry and artillery)
  • Brig. Gen. George D. Bayard’s Cavalry Brigade: 1st New Jersey, 1st Pennsylvania, and 1st Pennsylvania Rifles (last is an infantry battalion)
  • 3rd Maine Battery (as pontoniers)
  • Headquarters Guard: 2nd New York (Harris Light) Cavalry (remaining 2 companies)