Byron, IL has a population of 3,647 and is the 7,855th largest city in the United States. The population density is 1,020 per sq mi which is 359% higher than the Illinois average and 1026% higher than the national average. The median age in Byron is 36 which is approximately 5% lower than the Illinois average of 37. In Byron, 63% of the population over 15 years of age are married, 97% speak English and 3% speak Spanish. 72% of Byron residents were born in Illinois, 26% were born out of state, 1% were born outside of the United States and 2% were foreign born.