The Chicago Business Barometer, also known as the Chicago PMI, fell to 61.8 in November from 68.4 in the prior month. It is the lowest reading since February.
Economists polled by the Wall Street Journal forecast a 69% 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 November is released on Wednesday
Before the Chicago data, Lou Crandall, chief economist at Wrightson ICAP, said the regional manufacturing data released so far this month have signaled that manufacturing activity remained at a relatively strong level in November.
Economists surveyed by The Wall Street Journal have forecast a 61% reading for the closely-watched ISM manufacturing index in November after a 60.8% reading in the prior month.