Miamisburg, OH has a population of 20,168 and is the 2,122nd largest city in the United States. The population density is 1,655 per sq mi which is 486% higher than the Ohio average and 1727% 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, 64% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 75% of Miamisburg residents were born in Ohio, 23% were born out of state, 0% were born outside of the United States and 2% were foreign born.