Sheldon, IL has a population of 1,182 and is the 14,127th largest city in the United States. The population density is 1,575 per sq mi which is 609% higher than the Illinois average and 1639% higher than the national average. The median age in Sheldon is 37 which is approximately 2% lower than the Illinois average of 37. In Sheldon, 51% of the population over 15 years of age are married, 95% speak English and 5% speak Spanish. 81% of Sheldon residents were born in Illinois, 19% were born out of state, 0% were born outside of the United States and 0% were foreign born.