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Assay Office Museum
Assay office museum

James F. Bailey Assay Office Museum

The Assay Office Museum contains many tools and implements used in the assaying process, as well as furniture and artwork owned by the Bailey family. The museum is open the third Saturday of the month May through October.


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.


May through October
Third Saturday: 11 a.m. – 3 p.m.

Show Calendar

Admission & Tours

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

Getting There

The Assay Office is located west of Boulder in Fourmile Canyon

6352 Fourmile Canyon Dr
Boulder, CO 80302

360 Tour

Learn More About Hard Rock Mining

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

Hard Rock Mining Tours

Hard Rock Mining Tour

Tap into the towns, tools and characters of local hard rock mining heritage by visiting mining sites of years gone by. Tours are free but registration is required.

Upcoming Tours

Nederland Mining Museum

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.

Nederland Mining Museum

Virtual Hard Rock Mining Tour

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.

Virtual Hard Rock Mining Tour

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