Allendale, NJ has a population of 6,767 and is the 5,301st largest city in the United States. The population density is 2,185 per sq mi which is 218416% higher than the New Jersey average and 2312% higher than the national average. The median age in Allendale is 46 which is approximately 15% higher than the New Jersey average of 40. In Allendale, 70% of the population over 15 years of age are married, 85% speak English and 2% speak Spanish. 52% of Allendale residents were born in New Jersey, 35% were born out of state, 0% were born outside of the United States and 12% were foreign born.