Quinn says he could "see in the mess hall, in the chow halls, how united the soldiers are.
"This is one of the most difficult assignments ever in military history, and our soldiers and service members have done such an outstanding job," Quinn said.
The governor says he left on Friday morning from Andrews Air Force Base outside Washington and on Saturday met with U.S. military leaders in Baghdad.
Aides for Quinn say, for security reasons, they could not release where the governor was traveling next or when he would return to Illinois.
(The Associated Press contributed to this report.)