How can I get the rear wheel off?

I have a MTD 46" lawn tractor. It is about 16 years old. I need to take the wheel off to replace the tire, but the wheel is seems to be frozen. I took the pin out, and removed the key, but this thang will not move. I have tried all kinds of oil. I have tried a hammer, and got it to move a little, but this thing is stuck.