Old Mystic, CT has a population of 3,403 and is the 8,182nd largest city in the United States. The population density is 799 per sq mi which is 23% higher than the Connecticut average and 782% higher than the national average. The median age in Old Mystic is 45 which is approximately 12% higher than the Connecticut average of 41. In Old Mystic, 68% of the population over 15 years of age are married, 89% speak English and 2% speak Spanish. 43% of Old Mystic residents were born in Connecticut, 43% were born out of state, 2% were born outside of the United States and 12% were foreign born.