The Kessler Family Papers consists of five subgroups: Nickolas Kessler, Kessler Brewery, Kessler Brickyard, the Saloon, C.N. Kessler, and Nick Baatz Company.

The Kessler Brewing Company did not formally incorporate until 1901. Until that time Nickolas Kessler oversaw his business interests as an extension of his personal affairs. Because of this (and the fact that many of the letters are written in German), the letters pertaining to the brewery during Nickolas Kessler's lifetime were not separated from his personal correspondence. Correspondingly, Nickolas Kessler's personal financial records reflect his Commercial interests. Correspondence between Charles N. and Frederick Kessler dealing with their efforts to re-establish the brewery following repeal of national prohibition is found in the C.N. Kessler subgroup. The researcher interested in the brewery will find information in the Nickolas Kessler, C.N. Kessler, and Kessler Brewery Subgroups.

The Nickolas Kessler subgroup contains correspondence (1865-1900), which reflects Nickolas Kessler's personal and business interests and includes letters to and from other German-speaking immigrants and early Montana brewers, saloon keepers, and distributors; miscellaneous correspondence (1878) to Mrs. Nickolas Kessler; financial records (1865-1897), which pertain to Kessler's interest in his brewery, brickyard, saloon, real estate, as well as his personal finances; legal documents (1854-1898); subject files (1886-1893); miscellany; and clippings.

The Kessler Brewery subgroup consists of interoffice correspondence (1948-1952); incoming correspondence (1902-1920, 1936-1951); outgoing correspondence (1902-1919, 1933-1952); and general correspondence (1903-1904, 1933-1949). In addition, there are financial records (1865-1919); legal documents (1868-1933); minutes of the Montana Brewers Association (1916); photographs; printed materials (1905-1952); production records (1875-1919); reports (1901-1935); and miscellany.

The Kessler Brickyard subgroup is composed of financial records (1877-1901); production records (1892-1898); reports (1895-1896); and clippings.

The Saloon subgroup contains financial records (1880-1901).

The C.N. Kessler subgroup includes incoming, outgoing, and general correspondence (1893-1953) pertaining to his personal interests. There are, included in the letters between C.N. and Frederick Kessler, some dealing with their efforts to reinstitute the brewery following Repeal in 1933. There is a small amount of miscellaneous correspondence (1893-1942), letters neither to nor from C.N. Kessler, belonging primarily to other family members. There also are court papers (1949); legal documents (1903-1950); legislative materials (1909-1916) pertaining to Kessler's legislative duties and his efforts in the Legislative Assembly to combat prohibition; maps; printed materials (diverse dates) relating for the most part to the prohibition movement in Montana and elsewhere; reports (1916-1921) of Montana mining and oil activities; research notes (1892-1918) compiled by Kessler on brewing and Montana history; speeches (1911-1945); subject files (1910-1948); writings (1904-1935); and miscellany, which includes some materials belonging to the Kessler family children. In addition, there are numerous clippings collected by Kessler on topics of interest to him, including breweries, labor, mining, Montana, prohibition, oil exploration, etc.

The Nick Baatz Company subgroup consists of interoffice correspondence (1919-1922), incoming correspondence (1914-1922), outgoing correspondence (1918-1922), general correspondence (1922), and miscellaneous correspondence (1922). The subgroup also includes court papers (1922), financial records (1917-1923), legal documents (1922), subject files (1922), and miscellany.

There is a typed index to the collection at Montana Historical Society.