Walk to one end of the stone fence with a mason's hammer and chisel. Set the chisel in the cracks between the stones and chip away as much mortar as possible. Repeat this process until visible grooves are seen between each stone in the fence.
Stick the end of a pry bar in the grooves between the stones and pry the stones away from each other. Some will break free using this technique. For the ones that don't, go to Step 3.
Walk to one end of the stone fence with a sledgehammer and strike the topmost stone on the corner. Continue striking it until it breaks loose from the fence. Pick up the stone and carry it to a location out of the way. Return to the fence and strike the next stone. Work from the top to of the fence to the bottom. Remove each stone from the work area as you break them loose. Repeat this process until the fence has been removed.
Pick up all the small, broken fragments of stone and mortar and put them in a wheelbarrow. When the job is finished, no trace of the fence left should be left.
Put up a sign in your yard to either sell or give away the stones. Recycle some of them back into your yard or haul them to a quarry for reuse.