Glendale Heights, IL has a population of 34,395 and is the 1,226th largest city in the United States. The population density is 6,405 per sq mi which is 2781% higher than the Illinois average and 6970% higher than the national average. The median age in Glendale Heights is 33 which is approximately 11% lower than the Illinois average of 37. In Glendale Heights, 55% of the population over 15 years of age are married, 45% speak English and 26% speak Spanish. 52% of Glendale Heights residents were born in Illinois, 10% were born out of state, 2% were born outside of the United States and 36% were foreign born.