Gridley, IL has a population of 1,426 and is the 12,993rd largest city in the United States. The population density is 1,156 per sq mi which is 420% higher than the Illinois average and 1176% higher than the national average. The median age in Gridley is 42 which is approximately 13% higher than the Illinois average of 37. In Gridley, 72% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 84% of Gridley residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 2% were foreign born.