La Harpe, IL has a population of 1,459 and is the 12,852nd largest city in the United States. The population density is 1,070 per sq mi which is 381% higher than the Illinois average and 1081% higher than the national average. The median age in La Harpe is 40 which is approximately 6% higher than the Illinois average of 37. In La Harpe, 67% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 67% of La Harpe residents were born in Illinois, 33% were born out of state, 0% were born outside of the United States and 0% were foreign born.