Make sure your parking brake is not on.
Remove the brake cable from the hub.
Put a board over the end of the shaft and smack it with a large hammer. Only do it a couple of times. Then use the board to try and catch an edge and hammer on it. Rotate the hub every smack. If you can't rotate it, your brake is locked up.
Be careful when using pry bars, as there is a seal there that you don't want to damage.
If the brake is locked up, what I would do is make a mess. Plug the drain hole and fill the chamber with oil (cheap stuff will work fine). Put the wheel back on for leverage and turn it. Once you got it loosened up, take the wheel off and see if the drum will come off then.
If you use oil, you'll need to clean all the oil out of the entire chamber, use brake clean and soak the pads for a minute or two.
I should mention that I also used a rubber mallet. Specially formed, put an angle on the head so it would have more surface area for the angled strike.