This was once the assay office of the famous North London Mill located near timber line on the Mosquito Pass Road. It became part of South Park City in 1958. The large rough logs used in the construction of this building look out of place when compared to its overall size. Its sturdy construction is a reminder of the high winds and drifting snow it had to endure high on Mosquito Pass. One notes that the logs are not cut flat on the corners as is the case of the Garo log cabin. Large round nails helped hold the logs together. This was the minerís laboratory where the ore was tested and graded. After testing, prospectors and mine owners knew if the ore they were extracting was of commercial value. The North London Mine was one of the top gold producers in the South Park area. The mine was developed in the 1880ís and a mill was erected on the property soon after. It is assumed the Assay Office was erected sometime after 1890 due to its construction with round nails.
The Assay Office is furnished as it was during those rip-roaring gold rush days. The equipment was obtained from various mines in the area. The floor is dirt, as were most of the assay offices in Park County. Here one can see kilns, scales, crucibles and retorts (vessels within which ore was heated so that metal could be removed by distillation or sublimation). Chemicals lining the shelves were used for testing the purity and grade of the ore. A small handmade chair and table along with a potbelly stove are the only comforts in the office. Various rock samples including gold-bearing ore, copper, quartz, and crystals are displayed in a cabinet. Other rock samples on shelves along the walls include core samples as well as tongs for handling hot metal. The next stop is the Mill Building, with its displays of mining machinery.