Castle Station, as the post office was familiarly known, is one of the fanciest built in the United States. Through the efforts of Aaron T. Bliss (b. 1837), the U.S. Congress appropriated $100,000 in 1889 for construction of the post office. Civic leaders and the residents of East Saginaw rejected the first plans of the federal architects as unacceptably plain. Their demands for a new proposal yielded plans for this French Chateauesque building. The grayish-white Bedford limestone mass is accented with rounded towers and finials on every peak of its steeply pitched, red slate roof. Architect Aiken explained that the chateau style commemorated the early French settlers in Saginaw. The corner towers suggest the defensive feature of frontier life, while the carving of the pinnacles and finials draws its imagery from the fauna and flora of the area. Because of its “exclusive design, its rich trimmings, its imposing style,” the Saginaw Courier Herald for July 3, 1898, thought the government building the “handsomest in the United States.” Together with Hoyt Library (
SA5), the two formed a block that would serve forever “as an emblem of nineteenth century grandeur.” Charles W. Gindele of Chicago, under the supervision of George H. Miller, built the structure.

In 1937 the building was remodeled and enlarged. A rear tower was demolished to make room for the expansion of the workroom and lobby. The building currently houses the Castle Museum of Saginaw County History. The lobby remains intact, and exhibits occupy the workroom space.