Union County is a county located in the U.S. state of Ohio. As of the most recent data available, the county has a population of approximately 40,909 people, with a population density of about 93.61 persons per square mile.
The county spans a total land area of 437.00 square miles (1,132.00 square kilometers). The administrative center and county seat is Marysville, which often serves as a hub for local governance and services. The largest city within the county by population is Marysville.
Geographically, Union County experiences varied elevations, with its highest point at Milford Center 990 ft and its lowest point at Marysville 0 ft. The region operates in the UTC-5.