The Italianate-style Mansion was designed by Chicago architect John M. Van Osdel with a modified I-shaped configuration with a long central section stretching front to back.

The 16-room manor was completed in 1855 and was first occupied by governor Joel Matteson, who held the official grand opening on January 10, 1856.

The public libraries, bedrooms, parlors, sitting rooms, etc., are maintained in the style of the 19th century, blended with some later and modern pieces.

[5] Shortly after his election as governor, Bruce Rauner announced that he and his wife would invest some of their money into repairing the mansion so they could live in it during his term.

[5] On July 18, 2016, Illinois First Lady Diana Rauner announced a $15 million renovation project for the mansion, with the funding being raised privately.