Smithville, MO has a population of 9,069 and is the 4,231st largest city in the United States. The population density is 580 per sq mi which is 572% higher than the Missouri average and 540% higher than the national average. The median age in Smithville is 38 which is approximately equal to the Missouri average of 38. In Smithville, 65% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 60% of Smithville residents were born in Missouri, 38% were born out of state, 0% were born outside of the United States and 2% were foreign born.