The county seat is Celina, located ten miles from the Indiana border on U.S. 127 and State Routes 703 and 29.
Mercer County is located in the heart of what once was the Black Swamp area.
The once wet prairie is now covered with farmland growing corn, wheat, and beans. The county is steeped in history. Communities in Mercer County are clean. The area is proud of its German heritage. Many famous people have called Mercer County their home.