St. Louis, MI has a population of 7,302 and is the 5,029th largest city in the United States. The population density is 2,204 per sq mi which is 2085% higher than the Michigan average and 2332% higher than the national average. The median age in St. Louis is 34 which is approximately 14% lower than the Michigan average of 40. In St. Louis, 32% of the population over 15 years of age are married, 95% speak English and 4% speak Spanish. 86% of St. Louis residents were born in Michigan, 13% were born out of state, 1% were born outside of the United States and 1% were foreign born.