Thomasboro, IL has a population of 1,122 and is the 14,445th largest city in the United States. The population density is 1,126 per sq mi which is 407% higher than the Illinois average and 1143% higher than the national average. The median age in Thomasboro is 48 which is approximately 29% higher than the Illinois average of 37. In Thomasboro, 56% of the population over 15 years of age are married, 97% speak English and 0% speak Spanish. 80% of Thomasboro residents were born in Illinois, 17% were born out of state, 0% were born outside of the United States and 2% were foreign born.