During the landing roll at a remote airstrip, the pilot reported the airplane had slowed to about 25 knots, when the left main wheel collided with large rocks lining the left side of the landing area. The left main landing gear collapsed, and the left wing and propeller struck the ground. The left wing lift strut and wing were damaged, as were the propeller and fuselage. There were no known mechanical anomalies with the airplane prior to the accident.