As a captain, Davis was an assistant engineer on the construction project to build the Washington Monument, and was among the featured guests at the dedication ceremony in 1885.

It was Captain Davis who arranged and perfected all the elevating machinery that carried the stones one after another from the surface of the earth as they went up toward the sky.

It was his skill and rare ingenuity that invented the machinery which was so vitally important as a most efficient agent in the rapid and successful prosecution of the work.

In the important matter of strengthening and perfecting the foundation of the monument the suggestions and assistance of Captain Davis were invaluable.Afterwards, Davis became vice-president of the construction company that was to build the Nicaragua Canal and chairman of the international board of consulting engineers on the Panama Canal.

With the outbreak of the Spanish–American War, Davis was promoted to lieutenant colonel of regulars and brigadier general of Volunteers.