Ottawa, OH has a population of 4,430 and is the 6,985th largest city in the United States. The population density is 943 per sq mi which is 228% higher than the Ohio average and 941% higher than the national average. The median age in Ottawa is 39 which is approximately 2% lower than the Ohio average of 39. In Ottawa, 63% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 86% of Ottawa residents were born in Ohio, 13% were born out of state, 0% were born outside of the United States and 1% were foreign born.