Commander: Colonel James A. Mulligan

There were about 3,500 Union defenders present during the Battle of Lexington.

3rd Illinois Volunteer Infantry Regiment, "The Irish Brigade" - Colonel James A. Mulligan

14th Missouri Home Guard Regiment - Lt. Colonel Robert White

Lafayette Home Guard Battalion - Major F.W. Becker

13th Missouri Volunteer Infantry - Colonel Everett Peabody

1st Illinois Volunteer Cavalry - Colonel T.A. Marshall

U.S. Reserve Corps Infantry Battalion - Major R.T. Van Horn

27th Missouri Mounted Infantry - Lt. Colonel B.W. Grover

Volunteer Cavalry Battalion - Major M.P. Berry

The Muse South African