Harrisburg International Airport - about 20 mins away. If you will be renting a car, BWI or Philly are usually substantially cheaper but 90 minutes away.
Well, we were assuming he meant Penn State for medical school, in which case the campus is located in Hershey 12 miles from Harrisburg, not State College. If the OP is referring to the undergrad campus, then yes, the MAIN campus (there are many satellites) is in State College (Nittany Town).