The correspondence files consists of incoming and outgoing letters, some arranged chronologically, others by subject.

The managers letters are letters from the manager of the mine in Kellogg to the president of the company in San Francisco, detailing the operations of the mine, union activities, and related information. In 1892 the letters were from V.M. Clement to John Hayes Hammond; letters for 1893 are lacking; 1894- 1896 are from F.W. Bradley to N.H. Harris; 1897-1898, Frederick Burbidge to Bradley, also Bradley and Burbidge to Alex Granger; and 1899-1909 Burbidge to Bradley or Granger.

Then comes a general correspondence file, 1894-1900 which is an alphabetically arranged group (M-Z, 1898-1900, is lacking). The majority of these letters are inter-company correspondence between the Kellogg and San Francisco offices, although there are a few letters from suppliers.

Correspondence from stockholders contains both incoming and outgoing letters and is arranged alphabetically by the stockholder's last name. Most letters concern dividend payments, proxies, and stock purchases.

The F.W. Bradley correspondence files are arranged alphabetically by what appears to be the subject of the letter, although in some cases it is hard to tell. Letters were left in their original order. Most letters are from Bradley, as President as the company, to A. Burch and Frederick Burbidge and deal with routine company business.

The manager's letters of Stanly A. Easton, 1904-1926 (lacking May-December 1911 and January-March 1919) contain originals of Easton's letters to Bradley, carbon copies of letters from Easton to others which were enclosed in his letters, and copies of Bradley's replies. One file in this group concerns concentration and slips of paper in the main file refer to this concentration file, while slips in the concentration file refer to letters in the main group. For the years 1921 to May 1926 there is a separate file of carbon letters from Bradley to Easton. The letters from Easton to Jules Labarthe in San Francisco are original letters from Easton and carbons of Labarthe's replies. Most of these letters concern the cost of smelting.

A.A. Irish sold mining properties and his correspondence with Bradley, 1916-1928 concerns available mines.

Oscar A. Hershey was a geologist and consulting engineer who examined properties for Bunker Hill and Sullivan. His files, 1918-1929 contain originals of his letters to Bradley, carbons of his letters to Easton and carbons of Bradley's letters to him.

Easton's correspondence with the Alaska Juneau Gold Mining Company, 1925-1937 contains photocopies of Easton's letters which give information on Bunker Hill equipment and National Labor Relations Board hearings.

Urlyn Clifton Tainton was the electrometallurgist at Bunker Hill who designed the electrolytic zinc plant in 1926. His letters, 1920-1930, concern the treatment of ore.

The acid marketing correspondence, 1942-1954 and 1972 concerns Bunker Hill's supplying sulfuric acid to other industries.

The Employee and Public Relations Division file, 1955-1958, contains notices to employees concerning public relations matters. Carbons of letters to the department, and originals of letters from the personnel assistant and employee and public relations division manager are included.

Most of the letters in the Lead: Sales contract and correspondence file are to/from National Lead Company. Originals of letters from Nalco and carbons of letters to Nalco are included. The letters from Bunker Hill are signed by the Sales and Traffic manager; all letters concern the sale of lead and zinc to Nalco.

A note attached to the original bundle of Allied Chemical correspondence, 1952-1967, reads "Info was extracted from these files in response to a Justice Dept. inquiry re Allied Chem." Included are some original incoming letters and photocopies of outgoing letters which concern the sale of sulfuric acid.

E. Viet Howard's files, January-October 1979, contain photocopies of his correspondence, mostly inter office memoranda, concerning environmental issues.

The next group of correspondence is an alphabetical subject file, 1971-1981, maintained in the office of the president. Letters are both incoming and outgoing.

Finally there are letters between Frank Woodruff, President of Bunker Hill, and the Hecla Mining Company; correspondence with Hecla on the joint operation of the Star-Morning group, and financial settlements and progress reports of Hecla's work at the Star-Morning Mine.