Onarga, IL has a population of 1,295 and is the 13,573rd largest city in the United States. The population density is 1,097 per sq mi which is 393% higher than the Illinois average and 1110% higher than the national average. The median age in Onarga is 39 which is approximately 3% higher than the Illinois average of 37. In Onarga, 57% of the population over 15 years of age are married, 58% speak English and 39% speak Spanish. 63% of Onarga residents were born in Illinois, 13% were born out of state, 0% were born outside of the United States and 23% were foreign born.