The Chicago Business Barometer, also known as the Chicago PMI, dropped to 45.2 in October from 45.7 in the prior month, according to data released Monday.
Economists polled by the Wall Street Journal forecast a 47 reading.
Readings below 50 indicate contraction territory.
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 factory data for October is released on Tuesday.
Economist polled by the Wall Street Journal expect the closely-watched Institute for Supply Management’s factory index to barely remain above the 50 breakeven level in October.