Complex sentence: The easiest route is not "technical" during the summer season, and was probably first used by pre-Columbian indigenous people collecting eagle feathers, but the first recorded ascent was in 1868 by the surveying party of John Wesley Powell.
Split into simpler sentences: The easiest route is not "technical" during the summer season. The first ascent recorded by European Americans was in 1868 by the surveying party of John Wesley Powell.