On Dec 20, 1861 a resolution was passed in the U.S. Congress which stated in effect:
"Resolved, by the Senate and House of Representatives, that the thanks of Congress be presented to Col James A. Mulligan and the gallant officers and soldiers under his command who bravely stood by him against a greatly superior force, in his heroic defense of Lexington, Missouri. 116
“Resolved, That the 23rd Regiment of Illinois Volunteers - the Irish Brigade - in testimony of their gallantry on that occasion, are authorized to bear upon their colors the word. 'Lexington.'
“Resolved, That the Secretary of War be requested to communicate these resolutions to Col Mulligan and his officers and soldiers.
The joint resolution was ordered to be engrossed and read a third time and being engrossed, it was read a third time and passed.* (*from the Congressional Globe containing the debates and proceedings of the second session of the 37th Congress, page 158, Vol 1) 273