Watertown, CT has a population of 3,351 and is the 8,261st largest city in the United States. The population density is 1,582 per sq mi which is 144% higher than the Connecticut average and 1646% higher than the national average. The median age in Watertown is 48 which is approximately 18% higher than the Connecticut average of 41. In Watertown, 63% of the population over 15 years of age are married, 91% speak English and 4% speak Spanish. 77% of Watertown residents were born in Connecticut, 18% were born out of state, 1% were born outside of the United States and 4% were foreign born.