George Benson Nicholson was the civil engineer for the survey of the Virginia City and Lewiston Wagon Road project in 1866. Nicholson did two surveys, a course and distance survey of the Northern Nez Perces Trail (NNT) and a stake and chain survey for the wagon road survey. His survey of the NNT between Lolo, Montana and Green Saddle, Idaho was along the same trail followed by Lewis and Clark, except for a minor deviation between Moon Saddle and Indian Post Office. This document reports the research on his elevation profile and its extreme usefulness in finding the actual trail. Mathematical techniques were used to compensate for barometric altimeter variations due to weather. The research was completed before the discovery of Nicholson’s papers in the Ashland University Archives, Ashland, Ohio.