The Chicago Business Barometer, also known as the Chicago PMI, rose 4.8 index points to 48.6 in April.
Economists polled by the Wall Street Journal forecast a decline to a 43.8 reading.
This is the eighth straight reading below the 50 threshold that indicates 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. It is the last of the regional manufacturing indices before the national ISM data for April is released on Monday.
So far, the regional data suggest a modest improvement this month in the manufacturing ISM. In March, the ISM factory index fell to 46.3% from 47.7% in the prior month. It was the fourth month in contraction territory.