This building was the heart of the Oliver operation, the largest iron ore mining operation in United States history. The Superintendent of Mines and staff made day-to-day mining decisions here, supported by workers handling clerical work, payroll, record keeping, hiring and firing, and other administrative functions. After ore was mined, samples were crushed into fine particles and brought here for chemists to examine and determine iron content, which was used to calculate the ore's price and how it would be processed to make steel. The samples were then placed in containers, cataloged by where the ore was mined and by percentage of iron, and stored in sample houses behind the laboratory, alongside a sample crushing building, oil house, garage, and acid building.