Mahoning County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 238,823. Its county seat is Youngstown. The county is named for an Indian word meaning "salt lick". Mahoning County was formed on March 1, 1846; the 83rd county in Ohio. Until 1846, the area that is now Mahoning County was part of Trumbull and Columbiana counties, when the counties in the area were redefined and Mahoning County emerged as a new county.