On July 29, 2019, about 2040 mountain daylight time, a Cessna 150M airplane, Canadian Registered C-GEYP, was substantially damaged when it was involved in an accident near Roundup Airport (RPX), Roundup, Montana. The private pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot remembered flying cross-country that day starting from Oshkosh, Wisconsin. His previous stop before the accident was at Harding County Airport, (9D2), Buffalo, South Dakota, where he filled up with fuel. His final stop of the day was scheduled to be RPX, which was about 215.7 miles east-southeast of 9D2. The pilot recalled arriving in the local area of RPX about 2030. He mentioned that the airplane’s engine was “running fine” when he felt an impact, which was the last thing he remembered about the accident. He had no recollection of how he egressed from the airplane but remembered being found outside the airplane the next morning. The pilot further reported that there were no preimpact mechanical malfunctions or failures with the airplane. The accident site was located about 0.5 mile to the northwest of the approach end for runway 07. A review of the accident site pictures revealed that a tall tree was broken about 10 ft from the top, and the top portion of the tree was laying on the ground with a fresh break. A postaccident examination of the airplane revealed that it sustained substantial impact damage to the fuselage and wings. Flight control continuity was established. The engine was examined and was unable to be rotated due to the crankshaft being bent, which was consistent with impact damage. No other anomalies were noted during the examination of the engine or engine accessories that would have precluded normal operation. Sunset in Roundup, Montana, on the day of the accident was 2049.