Spearfish, SD has a population of 11,176 and is the 3,619th largest city in the United States. The population density is 679 per sq mi which is 6181% higher than the South Dakota average and 649% higher than the national average. The median age in Spearfish is 32 which is approximately 14% lower than the South Dakota average of 37. In Spearfish, 52% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 56% of Spearfish residents were born in South Dakota, 40% were born out of state, 1% were born outside of the United States and 3% were foreign born.