Dayton is a city in the U.S. state of Ohio and the county seat of Montgomery County, the fourth most populous county in the state. Dayton is the fourth largest metropolitan area in Ohio and the 61st largest Metropolitan Area in the United States. Dayton is within 500miles of 60% of the population and manufacturing capacity of the U.S. and so is defined as one of only two major logistics centroids in the United States. It plays host to significant industrial, aerospace, and technological/engineering research activity and is known for the many technical innovations and inventions developed there. With the decline of heavy manufacturing, Dayton's businesses have diversified into the service economy, including the insurance, legal, and healthcare sectors, though the city's population has continued to decline.