On January 23, 2003, at 2001 central standard time, a Cessna 210, N6572X, made a gear-up off airport landing following a loss of engine power. The forced landing took place near Clarence, Iowa. The private pilot and three passengers were not injured. The airplane was substantially damaged. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions. The last leg of the flight originated from Kirksville, Iowa, around 1840. The pilot reported he added a quart of oil and strained the fuel tanks prior to departing from Kirksville. He reported he was flying at 3,500 feet mean sea level (msl) when he encountered turbulence, so he decided to climb to 5,500 feet msl. He reported that while passing through 4,700 feet, the engine started sputtering and shaking. The pilot reported he switched fuel tanks, and adjusted the mixture, propeller control, and throttle. He stated the manifold pressure was indicating the high 20's and he was not sure if the engine was running. He reported the airplane was now at 3,700 feet and descending about 1,000 feet per minute. According to his global positioning system (GPS) the nearest airport was 9.8 miles away. After considering his landing options, the pilot elected to land in an area that was a "big black nothing." The pilot reported that he lowered the landing gear, but it did not engage in the down and locked position. He stated he was going to use the emergency extension hand pump, but he was getting low and decided to concentrate on flying the airplane. The pilot reported he turned his landing light on and "To my relief I saw a harvested cornfield; no sooner had my headlights illuminated the ground, I began to pull the nose up; I flared the airplane as well as I could." The pilot recalled the "roughness of sliding over the furrows of corn" and the airplane hitting a barbwire fence prior to coming to a stop. According to engine logbook records, the engine, a Continental IO-470-E, serial number 77543-O-E, had 1259.28 total hours when it was overhauled on June 30, 1971. The last logbook entry that listed a time since major overhaul (SMOH) for the engine was dated October 29, 2002. The time SMOH listed was 1237 hours. Total time on the airplane at the time of the accident was 2591.69 hours. Post accident inspection of the airplane was conducted by inspectors from the Federal Aviation Administration Flight Standards District Office in Des Moines, Iowa. One of the inspectors reported they had difficulty trying to turn the propeller by hand. He noted that there was a large amount of oil on the bottom of the engine cowling and no oil was found on the dipstick. The source of the oil leak was not determined. The inspector reported that further inspection revealed the crankshaft was broken between the number 2 and number 3 cylinders.