Alpena, SD has a population of 291 and is the 22,649th largest city in the United States. The population density is 179 per sq mi which is 1551% higher than the South Dakota average and 97% higher than the national average. The median age in Alpena is 48 which is approximately 29% higher than the South Dakota average of 37. In Alpena, 61% of the population over 15 years of age are married, 90% speak English and 10% speak Spanish. 60% of Alpena residents were born in South Dakota, 32% were born out of state, 0% were born outside of the United States and 8% were foreign born.