Marion, SC has a population of 6,756 and is the 5,308th largest city in the United States. The population density is 1,528 per sq mi which is 783% higher than the South Carolina average and 1587% higher than the national average. The median age in Marion is 35 which is approximately 11% lower than the South Carolina average of 39. In Marion, 45% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 85% of Marion residents were born in South Carolina, 14% were born out of state, 0% were born outside of the United States and 1% were foreign born.