On July 6, 1999, at 1645 central daylight time, a Cessna 177RG, N1937Q, piloted by a commercial pilot, sustained substantial damage during a forced landing near Weldon Springs, Missouri. The positioning flight was conducted under the provisions of 14 CFR Part 91 and was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The flight had departed from the Kirksville Regional Airport, Kirksville, Missouri, at 1545, and was en route to the Spirit of Saint Louis Airport (SUS), Saint Louis, Missouri. In a written statement, the pilot said that the airplane had just had maintenance performed which included an oil change and installation of a newly overhauled propeller and propeller governor. The pilot stated that, while en route, he noticed a loss of oil pressure. The pilot contacted the SUS tower controllers and informed them of the decreasing oil pressure. The pilot was transferred to a radar facility. Shortly after establishing communications with the radar facility, the aircraft engine failed and the pilot executed a forced landing in a field approximately 7 miles west of SUS. During the landing roll, the airplane struck trees at the end of the field. Post accident examination of the aircraft revealed damage to the lower fuselage substructure in the area near the door opening. Oil was found inside the engine compartment and on the exterior surfaces of the fuselage. No preexisting anomalies were detected.