The pilot reported that during the landing in the tailwheel equipped airplane, he executed a wheel landing, and continued to maintain directional control with the runway centerline. With the power at idle, the tail began losing lift and upon lowering the tail, the airplane began turning to the right. He applied left rudder, but found it ineffective so he also applied left brake to correct for the right turn. He was unable to bring the airplane back to the runway centerline, and felt that an aborted landing was no longer an option due to the direction the airplane was heading and the remaining runway length. He continued to apply left brake to the point where the tail began to lift, and tried to keep the airplane lined up to exit the runway at taxiway Delta. As the airplane entered the taxiway, the left main landing gear leg failed under side load. This resulted in the airplane’s left wing and fuselage contacting the runway surface as it came to rest with the airplane pointing about 45 degrees to the runway heading. The airplane sustained substantial damage to the left side of the fuselage. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.