The mansion was built in 1904 by 2 brother Michael and Timothy, who made there money by the lumber business, they married sisters Caroline and Elizabeth Metz and both couples would live at the mansion, each had there own enormous wing which was connected in the centre by a billiards room. Which were the main recreation point for their families and their friends. In the main stairs landing there is a small chapel where visitings priests would take mass. The brothers were also responsible for building Lake Mary, which provides the city with drinking water. Riordan Mansion now belongs to Arizona State park as the family donated their home and everything in it, to them. It is open for tours.

The upstairs of the mansion is said to be haunted by Caroline and her daughter Anna who have both been seen by staff and visitors.