Mendham, NJ has a population of 5,012 and is the 6,462nd largest city in the United States. The population density is 845 per sq mi which is 30% lower than the New Jersey average and 833% higher than the national average. The median age in Mendham is 48 which is approximately 21% higher than the New Jersey average of 40. In Mendham, 74% of the population over 15 years of age are married, 89% speak English and 4% speak Spanish. 62% of Mendham residents were born in New Jersey, 30% were born out of state, 2% were born outside of the United States and 6% were foreign born.