Interlaken, NJ has a population of 806 and is the 16,555th largest city in the United States. The population density is 2,433 per sq mi which is 243236% higher than the New Jersey average and 2586% higher than the national average. The median age in Interlaken is 57 which is approximately 45% higher than the New Jersey average of 40. In Interlaken, 69% of the population over 15 years of age are married, 94% speak English and 1% speak Spanish. 66% of Interlaken residents were born in New Jersey, 28% were born out of state, 1% were born outside of the United States and 5% were foreign born.