The Chicago Business Barometer, also known as the Chicago PMI, fell to 56 in June from 60.3 in the prior month.
Economists polled by the Wall Street Journal forecast a 58 reading.
The index is produced by the ISM-Chicago with MNI. It is released to subscribers three minutes before its release to the public at 9:45 am Eastern.
The Chicago PMI is the last of the regional manufacturing indices before the national ISM data for June is released on Friday.
So far this month, the regional manufacturing surveys released by Federal Reserve banks have shown a deterioration in business sentiment even as measures of activity have been positive.
Economists surveyed by the Journal have forecast a 54.3% reading for the closely-watched ISM manufacturing index in June after a 56.1% reading in the prior month.
