Miamisburg, OH has a population of 20,069 and is the 2,173rd largest city in the United States. The population density is 1,644 per sq mi which is 538% higher than the Ohio average and 1715% higher than the national average. The median age in Miamisburg is 41 which is approximately 5% higher than the Ohio average of 39. In Miamisburg, 62% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 76% of Miamisburg residents were born in Ohio, 22% were born out of state, 0% were born outside of the United States and 2% were foreign born.