The records of the Northern Chief Iron Company contain a wealth of material pertaining to the company's involvement in the iron ore mining industry on the Gogebic range and span from 1874 to 1977. The collection is divided into three series: Administrative Records, Mining Companies, and Financial Records. The Administrative Records provide documentation on the development of the company, its relationship with mining and railroad companies, and land purchases and disputes. The Mining Companies series includes leases, agreements, monthly reports, and correspondence that document communication between Northern Chief and mining companies, mostly Montreal Mining Co. and Odanah Iron Co., and traces the development and production of the mines. The Financial Records provide a glimpse into the financial history of the company as well as documenting lands owned and leased to individuals.

The ADMINISTRATIVE RECORDS consist of Correspondence; Deeds, Patents, and Quit Claims; Railroad Quit Claims and Mine Tracks; and records from Court Cases concerning land disputes. The correspondence files document the beginnings of the company as well as its progression over the years. Correspondence between Gile, the first treasurer, and Plumer, the first president, focuses on negotiations with current and prospective iron companies concerning leases, reports on mining operations, and the company's financial situation. General Correspondence (1895-1896) contains letters from mining companies concerning existing contracts and negotiations with those interested in leasing properties as well as the climate of the mining industry. Mine Reports from Robert King, on-site caretaker, provide a wealth of information on the conditions of the Cary, Windsor, Superior, Germania, and Minnewawa mines, including number of men employed, amount of ore hoisted, repairs and developments, and equipment used. The correspondence of Thomas Bardon and A. J. and F. W. McKay, all directors, discuss the value of ore, determination of royalties, payments of dividends, decisions made at director meetings, and mine strikes and the climate of the mining industry. Correspondence of Hugh Roberts, mining geologist and independent consultant from Duluth, and Clyde Holmberg, mining engineer from Ironwood, Michigan, deal with estimates of remaining ore, mine visits to Cary and Montreal mines, and shipments and production.

The Deeds, Patents, and Quit Claims document the purchasing of lands from 1874 to 1886 during the land rush on the Gogebic iron range. There are also a few records from the 1920s. The Railroad Quit Claims and Mine Tracks document how Northern Chief Iron Company transferred property claims to railroads to provide transport for the ore, demonstrating the co-dependence of the iron ore industry with the northward expansion of the railroad. The Court Cases concern land disputes and include litigation on the clearing of titles to ore lands. In the 1880s some titles and land deeds held by Northern Chief were lost through tax sales and fraud.

The MINING COMPANIES series consists of Mining Company Leases and Agreements and Mine Reports made for Northern Chief from various mining companies, principally the Montreal Mining Company and the Odanah Iron Company. The Mining Company Leases and Agreements record the financial terms of the lease and provide the location of land leased. The Mine Reports contains reports submitted to the company. The ledger (1896-1900) lists ore contracts, report of sales, shipments, railway reports, analysis of ore, and statement of royalties for Germania, Cary, Windsor, Minnewawa, and Pence mines. The monthly reports, written by Clyde Holmberg, give an account of development work being done at the mines, the levels being mined, and include detailed dimensions and locations. The annual reports, written by Clyde Holmberg and Hugh Roberts, document production, shipments, estimated remaining ore, analysis of ore, tons in stockpile, and exploration. The reports are most extensive for the Montreal Mining Company and the Odanah Iron Company. These reports consist of statements of shipment including type of ore, tonnage, who the ore was shipped to and by which railroad, selling price, and royalty statements.

The FINANCIAL RECORDS consist of Income and Tax Information, Stockholder Information, Hurley Sales and Tax Deeds, and Correspondence. The Income and Tax Information documents the companies earnings from 1917 to 1936. The Stockholder Information contains limited information on stockholders and dividends paid out. The records in Hurley Sales and Tax Deeds list the plot, who the plot was sold or deeded to, and the present owner. The Correspondence files include Tax Certificate Correspondence that consists of letters from M. F. Reid and E. H. Reid, lawyers in Hurley, dealing with tax certificates and lots held by the Northern Chief Iron Co. and leased to individuals. Many of the letters include narratives describing the circumstances of lessees. Financial Correspondence is mostly letters from stockholders but includes a financial report from 1943 and a 1968 Annual Meeting Report announcing partial liquidation of the company. Correspondence with the IRS also deals with the 1968 partial liquidation as well as questions on determination of tax.