If you mean a utility type with the one piece rim & center... Probably just a little rusty and hung up. Spray some penetrant around the center hole, and lug holes, maybe some in from the back if possible, and let soak a bit. I'm assuming the tire is flat, but you can still bump the tire with a sledge, alternating front and back. If totally flat, maybe a block of wood on the rim, and bump it the same way. If there is room, bump it from the backside.
A good cleaning when you get it removed, and some never seize when you put the wheel back on may save a lot of time, in case it needs done again in the future.
The center bolt should be the hub retainer bolt, and I believe not necessary to remove the wheel.