Amazingly, while the staircase itself was missing, an incredible amount of evidence that revealed what the stairs looked like survived on the walls, floors and ceiling of the North Passage.  Additionally, a fairly large fragment from one of the ca. 1797 newel posts was discovered in the framing of a ca. 1848 pilaster which had replaced one of the ca. 1797 Madison pilasters when the Portico was renovated.  Finally, the Restoration Team also investigated other surviving ca. 1797 stairs from Virginia to determine how stairs were trimmed in general during the period.  When the investigations were finished, the evidence collected allowed the Restoration's architects to design a new stair for the North Passage that accurately reflected the stair that was found in the passage in Madison's time.