Grayslake, IL has a population of 21,053 and is the 2,061st largest city in the United States. The population density is 1,932 per sq mi which is 769% higher than the Illinois average and 2032% higher than the national average. The median age in Grayslake is 38 which is approximately equal to the Illinois average of 37. In Grayslake, 60% of the population over 15 years of age are married, 81% speak English and 9% speak Spanish. 61% of Grayslake residents were born in Illinois, 25% were born out of state, 1% were born outside of the United States and 13% were foreign born.