Slippery Rock, PA has a population of 3,620 and is the 7,887th largest city in the United States. The population density is 2,200 per sq mi which is 694% higher than the Pennsylvania average and 2328% higher than the national average. The median age in Slippery Rock is 22 which is approximately 46% lower than the Pennsylvania average of 41. In Slippery Rock, 23% of the population over 15 years of age are married, 96% speak English and 0% speak Spanish. 73% of Slippery Rock residents were born in Pennsylvania, 23% were born out of state, 1% were born outside of the United States and 3% were foreign born.