Lake Bluff, IL has a population of 5,758 and is the 5,908th largest city in the United States. The population density is 1,413 per sq mi which is 536% higher than the Illinois average and 1459% higher than the national average. The median age in Lake Bluff is 46 which is approximately 23% higher than the Illinois average of 37. In Lake Bluff, 73% of the population over 15 years of age are married, 90% speak English and 1% speak Spanish. 55% of Lake Bluff residents were born in Illinois, 35% were born out of state, 2% were born outside of the United States and 8% were foreign born.