The building, a large, wooden, white, two-story structure in the Queen Anne style, was built originally as a private residence for local merchants.

On July 23 of that year, Cass Gilbert was chosen to direct construction for the new complex, which was to include a capitol building as well as an executive mansion.

The work was overseen by local architect Walter F. Martens, but he was not greatly involved in the design of the neighboring capitol building.

[2] However, Martens had traveled to New York City to talk with Gilbert about designs for the project, and both had similar ideas for the building's Georgian style.

[3] His visit allowed him to learn how to create a floor plan able to accommodate heavy traffic of guests, as many as 2,000 visitors at once.

[3] The building's first occupant, Ephraim F. Morgan, who had first proposed to the state the construction of a new residence,[3] only lived in the new mansion for one week because his term expired during 1925.

[2][3] From 1965 to 1969, during the term of Hulett C. Smith, the mansion underwent a thorough renovation process, with a total of $300,000 spent in both structural improvements and historic preservation efforts.