The Riordan Mansion State Historic Park is a state historic site featuring the Riordan Mansion, a historic pseudo duplex building that was home to Timothy and Michael Riordan, brothers, who married sisters Caroline and Elizabeth Metz.

The house features over 13,000 square feet of living area cleanly divided into two similar wings adjoined by a large common room. The house was designed by Charles Whittlesey, also the architect of the El Tovar Hotel at the Grand Canyon. It is considered as one of the greatest examples of Arts and Crafts style architecture in the state.

Today, the Mansion I s treated as a historical museum featuring the history of the building and the families that built and lived within it.