Rensselaer, MO has a population of 222 and is the 23,969th largest city in the United States. The population density is 114 per sq mi which is 31% higher than the Missouri average and 25% higher than the national average. The median age in Rensselaer is 44 which is approximately 15% higher than the Missouri average of 38. In Rensselaer, 65% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 74% of Rensselaer residents were born in Missouri, 26% were born out of state, 0% were born outside of the United States and 0% were foreign born.