James F. Bailey Assay Office Museum

James F. Bailey Assay Office Museum

At the turn of the twentieth century, hard rock mining in Boulder County was in full swing, and the area known as Wall Street played a prominent role in this chapter of our community's history. The assay office was the place where prospectors would take their ore samples to find out whether or not they had potentially "struck it rich." So important was the determination of the assayer that the results of their work could, and often did, make or break a prospector.

Getting There

The Assay Office is located west of Boulder in Fourmile Canyon 
6352 Fourmile Canyon Dr
Boulder, CO 80302
Map & Directions

Museum Hours

  • July 18: 10 a.m. - 2 p.m.
  • August 15: 10 a.m. - 2 p.m.
  • September 19: 10 a.m. - 2 p.m.
  • October 17: 10 a.m. - 2 p.m.


Tours for groups of 12 or more people are available by appointment mid-April through mid-October.


Admission is free.

Learn More About Hard Rock Mining

The Assay Office is just one of many ways Boulder County preserves our mining history.

Hard Rock Mining Tour

Take a virtual tour of Boulder County's mining history. A map shows locations and information about the prominent mines of this area. The Switzerland Trail Railroad also gets special attention for its role in the mining industry and life in Boulder County in general.

Nederland Mining Museum

Visit the Nederland Mining Museum and get a glimpse into the world of hard rock mining days in Boulder County during the late 19th and early 20th centuries. Learn about the lives of the miners of yesteryear.

In-person Hard Rock Mining Tours

In-person Hard Rock Mining Tours are offered several times throughout the summer. Spend a morning or afternoon with a tour guide to visit and learn about fascinating historic mining sites of Boulder County. Check the calendar for upcoming tours.


Parks & Open Space
Sheryl Kippen