Statement of Significance (as of designation - December 30, 1970):
Erected between 1848 and 1868, this is a prototypical example of the French Renaissance chateauesque style of great mansions of the Gilded Age. Its scale and materials represent a new standard of opulent display for the era. The mansion's rooms are arranged around a central octagonal rotunda lighted by a four-story skylight.

The museum has applied for a 2004 Save America's Treasures grant to install climate control systems to protect the extensive veneers, hand painted embellishments, marquetry and wood carvings, and other elaborate finishes in the 62-room mansion.