Merrillville, IN has a population of 35,268 and is the 1,194th largest city in the United States. The population density is 1,062 per sq mi which is 492% higher than the Indiana average and 1072% higher than the national average. The median age in Merrillville is 38 which is approximately 2% higher than the Indiana average of 37. In Merrillville, 49% of the population over 15 years of age are married, 90% speak English and 7% speak Spanish. 59% of Merrillville residents were born in Indiana, 35% were born out of state, 1% were born outside of the United States and 5% were foreign born.