Technically, you were a Maryland resident until you moved to Pennsylvania. For that period of time you should file a Maryland part-year resident tax return and pay tax in Maryland. When you moved to Pennsylvania, from that time until the end of the year you should file a Pennsylvania part-year resident tax return. The problem is your W-2 form is going to show Pennsylvania income for the total time you worked there, so you need to look for a credit for taxes paid to another state when you do you PA tax return so you will get a deduction for taxes paid to Maryland.
It would be best to do your Maryland tax return first, so you will know what your Maryland tax is as you'll need to enter that to get credit for it on your Pennsylvania tax return.