The pilot reported being approximately 7,200 feet, 3 miles south of the airport, when the airplane's engine began to run rough. The pilot turned back toward the airport and then determined that he would not be able to reach it. About that time, the engine "stopped completely." The pilot decided to attempt a forced landing to a hilly pasture. During the forced landing the airplane impacted the rough terrain, the landing gear sheared off, and the right wing bent upward approximately 3 feet inboard of the tip. Inspectors at the scene reported the right wing was also broken aft at the wing root. The pilot and passenger sustained minor injuries. An examination of the airplane showed the left wing fuel tank empty. The right wing fuel tank showed some residual fuel. The airplane's fuel selector valve was positioned to the left wing fuel tank. Flight control continuity was confirmed. An examination of the engine, engine controls, and other airplane systems showed no anomalies.