They work for Prime, which this week announced it is shutting down labor and delivery services at three area hospitals.
Nurses that are on strike said they are concerned about patient care and staffing.
This is part of a larger strike across three states.
Here locally, rallies are expected outside Saint Mary of Nazareth Hospital and Olympia Fields Hospital. All of them are owned by Prime Healthcare.
RELATED: 3 hospitals in suburbs, Chicago to stop delivering babies, giving neo-natal care: Prime Healthcare
This one -day strike at Saint Mary's also comes as Prime Healthcare is closing or consolidating birthing services at some hospitals in the Chicagoland area.
Thursday morning, nurses picketed outside Saint Mary of Nazareth Hospital.
Nurses there unionized in June and are striking to for what they call a fair first contract.
"We are pushing for safer working conditions in the hospital and a clear contract that will allow us to retain the skilled nurses that we need to properly care for our patients," Elena Davis, a registered nurse, said.
Union organizers also accuse the hospital of firing nurses as they were trying to unionize.
Thursday, Mayor Brandon Johnson stopped at Saint Mary's Hospital to show his support for the nurses that are on strike.
"As a proud union town , at a moment in which affordability is the top issues for families across America, it's unconscionable that this for-profit entity has placed profit over the needs of people and so I'm encouraging our nurse and the entire city of Chicago to stand with our nurses to ensure they have a fair contract," Johnson said.
In a statement in part a hospital spokesperson for Prime Healthcare says, "Saint Mary of Nazareth Hospital is committed to bargaining in good faith with the union representing some of its nurses, with the goal of reaching an agreement that supports our employees while protecting our ability to provide safe, high-quality care to the patients and community we serve."
Saint Mary's said the one-day strike is not expected to disrupt patient care and the hospital will remain open and staffed.