Friday was the first of five shutdown days for the county government, designed to help close the huge budget deficit.
Most departments were closed, including 16 county health clinics and three hospitals.
Hospital emergency rooms remained open. The Cook County Board of Review, Courts, and the County Jail are also open.
Four more shutdown dates are coming up in May, July, September and November.
Many nurses are outraged by the furlough days. They claim patients are being put at risk.
"We are here today to tell Cook County to be true to your mission statement, and that mission statement is to take care of the patient regardless of the ability to pay and the budget," said Martese Chism, R.N., Stroger Hospital.
Nurses are upset because they say no one told patients their clinics would be closed, and some came seeking treatment, only to find the facilities were locked.