Marshall, IL has a population of 3,536 and is the 7,997th largest city in the United States. The population density is 948 per sq mi which is 327% higher than the Illinois average and 946% higher than the national average. The median age in Marshall is 39 which is approximately 5% higher than the Illinois average of 37. In Marshall, 57% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 41% of Marshall residents were born in Illinois, 58% were born out of state, 0% were born outside of the United States and 1% were foreign born.