There are 1 US Post Offices in Ohio County serving a total of 5,480 residents equating to 5,480 residents per post office. It's estimated that approximately 8,747 packages are handled across the 1 county post offices annually. Ohio County is a county located in southeastern Indiana. As of 2010, the population was 6,128. The county seat and only incorporated municipality is Rising Sun. The county was officially established in 1844 and was one of the last Indiana counties to be created. It is the smallest county in the state in terms of both area and population. Ohio County borders the state of Kentucky across the Ohio River for which it was named. It is part of the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area. The county is divided into four townships which provide local services. Three state roads pass through or into the county."