Jefferson, OH has a population of 3,295 and is the 8,339th largest city in the United States. The population density is 1,299 per sq mi which is 404% higher than the Ohio average and 1334% higher than the national average. The median age in Jefferson is 37 which is approximately 6% lower than the Ohio average of 39. In Jefferson, 55% of the population over 15 years of age are married, 96% speak English and 2% speak Spanish. 80% of Jefferson residents were born in Ohio, 17% were born out of state, 1% were born outside of the United States and 2% were foreign born.