Assuming the property is in PA and that you are a resident of PA, then you will owe both federal and state taxes on any gains realized on the sale. Typically, if you pay the tax in the quarter you sell the property, there's no issues dealing with things like underpayment penalties at tax filing time.
Check out https://www.revenue.pa.gov/Tax%20Rates/Pages/default.aspx for state tax rates.
