Adams County lies in northeastern Indiana in the United States and shares its eastern border with Ohio. It was officially established in 1836. The county seat is Decatur. According to the 2020 census, its population was 35,809, an increase of 4.1% from 34,387 in 2010. The county has four incorporated cities and towns with a total population of over 15,000, as well as many small unincorporated communities. The county is divided into 12 townships which provide local services.