A majority of the evidence used to reconstruct the structural elements of the stair were found on the walls, floors, and ceiling of both the first and second floors of the North Passage.  Because almost all of the stair's structural elements were based on physical evidence found in the Mansion, the form of the reconstructed stair is very similar to what Madison built in ca. 1797.  To be successful, the investigation of the physical evidence needed to recover the stair's four fundamental characteristics: where the stair started, where it stopped, the slope of the stair and the height of the stair's landing.