The pilot was landing in a tailwheel-equipped airplane at a remote, rough and uneven off-airport site, which required a correction for a 15 to 20 mph left crosswind. He stated that during the landing roll the wind pushed the airplane to the left, which resulted in a side load on the main landing gear, and the right main landing gear wheel axle separated. The right wing subsequently struck the ground, sustaining substantial damage. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.