Westerville, OH has a population of 38,089 and is the 1,091st largest city in the United States. The population density is 3,026 per sq mi which is 1075% higher than the Ohio average and 3240% higher than the national average. The median age in Westerville is 41 which is approximately 5% higher than the Ohio average of 39. In Westerville, 63% of the population over 15 years of age are married, 94% speak English and 2% speak Spanish. 69% of Westerville residents were born in Ohio, 26% were born out of state, 1% were born outside of the United States and 5% were foreign born.