On August 30, 2016, about 2035 central daylight time (CDT), a Cessna 150L airplane, N18601, impacted terrain short of the grass runway at Rosenau Airport (21ND), Upham, North Dakota. The private pilot, the sole occupant, suffered serious injuries and the airplane was substantially damaged. The airplane was privately registered and operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. The local flight departed from 21ND about 1900. The pilot reported that he was returning from a local pleasure flight and was approaching his unlighted, grass airstrip to land to the west, and into the setting sun. He said the sun had already set, but there was light to the west. He did not remember the crash. The airplane impacted a river bank near the approach end of the runway, 6 ft below the elevation of the runway, nosed over and traveled 42 ft before coming to rest upside down. Sunset occurred at 2032 and civil twilight ended at 2104. Examination of the airplane showed that the fuselage was buckled behind the cockpit and the left wing spar was bent. The pilot indicated on his submitted NTSB Accident/Incident report there were no malfunctions with the airplane prior to the accident. According to the Federal Aviation Administration, the pilot did not hold a current medical certificate. The pilot's reported last medical examination was for a third class medical on May 5, 2012. The last annual inspection of the airplane was November 30, 2013. No pilot or maintenance logbooks were recovered during the investigation.