This collection primarily contains correspondence, diaries, religious materials, and legal documents of the Warren family of Three Oaks, Berrien County, Michigan. The bulk of the correspondence consists of letters (1879-1899) from Albert L. Warren to his parents (Caroline C. and Rev. Waters Warren) and brothers (Edward K. and Frederick P.). Albert L. Warren was an itinerant watch repairman who tried prospecting gold, teaching, farming, selling wholesale groceries and later patent medicine, and manufacturing jewelry. These endeavors led him over most of California and Oregon as well as Idaho, Nevada and Arizona Territories. Especially interesting is the description of the Idaho gold fields and the overland journey to reach them. In the letters are reports on mining, social life, agriculture, and business conditions of the different areas.

Other correspondence includes letters (1870-1888) from Edward K. Warren, many of which concern the Warren Brothers Calculating Engine invented by Frederick P.; letters (1864-1865) from Frederick P. Warren describing his life as a soldier in Company E, 12th Regiment of the Michigan Infantry during the Civil War; the correspondence (1853-1870) of Rev. Waters Warren with other evangelists; some of the business correspondence (1885-1915) of the Warren Featherbone Whip Company, founded by Edward K. who invented the process of featherboning (using turkey feathers rather than whalebone for women's dress stays); and a handwritten letter (January 14, 1863) from Zachariah Chandler to Rev. Waters Warren. See E. K. Warren correspondence for 1895 letter of evangelist Dwight L. Moody. The Civil War letters have been transcribed, scanned and placed online at http://civilwar.archives.msu.edu/collection/7-1C-44/warren/.

Also included is a series of letters from New England from Charles K. Warren to his parents. The letters span the years 1879-1889 when Charles was attending Mt. Herman and Elmwood Schools. The letters give many details on conditions in New England boarding schools in the later 19th century, as do several letters from Edna Warren who also wrote from a New England boarding school in Worchester, MA in 1889.

Other materials in the collection consist of information (1878-1924) about the World's Sunday School Conventions which were attended by Edward K. who was chairman of the executive committee; foreign missionary materials (1874-1920); patent materials (1862-1869) and undated) on Waters Warren's beehive; diagrams (1875) of Frederick P. Warren's calculating machine; tax receipts (1860-1878); family diaries and manuscript materials; and newspaper clippings and articles (1872-1935) primarily about Edward K. Warren.

A collection of glass plates is included in the collection which deals with the following topics: Business and Industry; People (portraits and groups); Places and Scenes (Michigan, United States, and Foreign); and Art - Reproductions of paintings and etchings. Included in the glass plate negatives are several images from the Dewey Cannon dedication on October 17, 1899. The Dewey Cannon is an antique Spanish bronze cannon that was captured by the United States Navy in 1898 after the Battle of Manila Bay. It was used by the U.S. as a fund-raising drive and awarded to Three Oaks for raising more money per capita than any other town. President William McKinley attended the dedication ceremony.