The pilot reported that he checked the fuel level by looking at the fuel gauge prior to departure, and it read about 1/2 tank. Approximately one hour after departure, the pilot was beginning to make a descent to the destination airport. About 3 miles from the airport the engine quit, and the pilot executed a forced landing to a road. During the approach to the road, the stall warning sounded as he tried to clear some trees. He lowered the nose and flew under the trees, but the left wing hit a tree and the airplane impacted the ground. An inspection of the airplane revealed that there was about 1.5 gallons of fuel remaining in the tanks. The Pilot Operating Handbook states that the unusable fuel capacity of the airplane was 3.5 gallons.