LaSalle, IL has a population of 9,484 and is the 4,100th largest city in the United States. The population density is 737 per sq mi which is 232% higher than the Illinois average and 714% higher than the national average. The median age in LaSalle is 39 which is approximately 3% higher than the Illinois average of 37. In LaSalle, 49% of the population over 15 years of age are married, 92% speak English and 7% speak Spanish. 81% of LaSalle residents were born in Illinois, 13% were born out of state, 1% were born outside of the United States and 5% were foreign born.