Bethalto, IL has a population of 9,364 and is the 4,139th largest city in the United States. The population density is 1,245 per sq mi which is 460% higher than the Illinois average and 1274% higher than the national average. The median age in Bethalto is 38 which is approximately 2% higher than the Illinois average of 37. In Bethalto, 66% of the population over 15 years of age are married, 95% speak English and 1% speak Spanish. 77% of Bethalto residents were born in Illinois, 20% were born out of state, 1% were born outside of the United States and 2% were foreign born.