Monmouth Junction, NJ has a population of 3,199 and is the 8,486th largest city in the United States. The population density is 2,141 per sq mi which is 213965% higher than the New Jersey average and 2263% higher than the national average. The median age in Monmouth Junction is 39 which is approximately 2% lower than the New Jersey average of 40. In Monmouth Junction, 65% of the population over 15 years of age are married, 54% speak English and 1% speak Spanish. 39% of Monmouth Junction residents were born in New Jersey, 23% were born out of state, 1% were born outside of the United States and 37% were foreign born.