The head of Cook County’s hospital system is quitting his post.

William Foley has led the country’s third largest public health system since 2009. In a statement yesterday, he did not give a reason for stepping down.

Foley’s announcement comes as he’s been pushing a controversial move to close a county hospital in Chicago’s south suburbs. Earlier this week, Illinois officials rejected the idea to close Oak Forest Hospital and turn it into an outpatient center.

In a statement, County Board President Toni Preckwinkle praises Foley for improving the health system’s finances.

The Cook County Health and Hospitals System’s board of directors is expected to appoint an interim CEO on Friday.