They say it's a number many people know, but might not know how to use properly.
A new campaign through OSF St. Joseph Medical Center is trying to get people to always call 911 in an emergency as opposed to driving.
Officials say sometimes people think driving is cheaper or quicker, but they say that's not the case.
They say calling 911 allows first responders at the hospital to be ready and waiting for when an ambulance arrives.
When it comes to heart attacks and strokes, driving yourself could hurt not only your recovery changes, but also innocent bystanders.
"You are risking losing that muscle in your heart. You're also risking damage to your brain. You're also risking lives of others and yourself. You could have a car accident. You could have worsening sympathies actually on your way to the hospital," said Lisa Stevens, OSF St. Joseph Medical Center's Director of Radiology.
On the flip side, abusing 911 is against the law.
Police say they can arrest you for making prank calls or filing false reports.