During the
expansion of the railroads in the U.S., Hamilton maintained over 56% of
the market. Railroads purchased all of Hamilton's production. As the
market switched from pocket watches to wrist watches after World War I,
the company manufactured wrist watches. During World War II, Hamilton
retooled its business model to serve the military, dropping its consumer
products.
The Illinois Watch Co. is purchased by Hamilton
Watch Co. following the death of company president Jacob Bunn, Jr. The
factory continued operations in Springfield, Illinois until 1932.
Illinois movements continued to be finished at the Hamilton factory
until 1948.