Plankinton, SD has a population of 679 and is the 17,668th largest city in the United States. The population density is 899 per sq mi which is 8217% higher than the South Dakota average and 892% higher than the national average. The median age in Plankinton is 44 which is approximately 20% higher than the South Dakota average of 37. In Plankinton, 72% of the population over 15 years of age are married, 85% speak English and 15% speak Spanish. 68% of Plankinton residents were born in South Dakota, 19% were born out of state, 1% were born outside of the United States and 13% were foreign born.