Correspondence (1855-1865) related to Hans Mattson's service in the Civil War is very complete. Mattson enlisted as a captain of Company D, 3rd Regiment, Minnesota Veteran Volunteer Infantry (October 1861) and eventually became the regiment's colonel. The letters (some in Swedish) are from Mattson to his wife in Red Wing. They describe camp life; marches; cities and towns in the South, particularly Little Rock, Arkansas; and Mattson's experiences as a commander of a military district in the area of Batesville, Arkansas following the war. The regiment was mustered out of service in September, 1865. Included in this correspondence is a letter from General Robert E. Lee to Major General J.A. Early, dated January 21st, 1864 regarding the acquisition of cattle for the army and in a postscript, the presence of troops near the Rapidan River.

The next years (1866-1881) contain only a few letters for each year. Topics include Mattson's editorship of the newspaper Svenska Amerikanaren, Chicago (1866 1867); his work as secretary of the Minnesota Board of Immigration (1867); and his service as head of the Land Department, St. Paul and Pacific Railroad Company, and the development of land near Litchfield (Meeker County), Minnesota (1868). Other items of interest include some letters (in Swedish) from Sweden (1869); a certificate of dismissal (1870) from the Scandinavian Evangelical Lutheran Church of Red Wing to Hans and Kjersti (Perrson) Mattson, also containing vital statistics information on members of the Mattson family; a small notebook kept by Mattson while on a trip to Sweden (1873, partially written in Swedish); and a certificate (November 26, 1876), signed by Governor John S. Pillsbury, certifying Mattson's election as a presidential elector.

Correspondence (1881-1883) covering the period when Mattson was Consul General of the U.S. in Calcutta, India, is more complete. The letters are from Mattson to his wife and children, and contain descriptions of Mattson's ocean voyage from England to India; his work as Consul General; social customs in India; his activities as a member of the Calcutta Literary Society; and personal and financial problems of the Mattson family. Items of interest include two letters (Nov. 23, 1881 and February 2, 1882) to Mattson from the Indian author Sourindro Mohun Tagore; a booklet containing the annual report of the Calcutta Literary Society (January 28, 1882); two letters (August 17 and September 1882) from Mattson to his sons containing the story of Mattson's life; letters (November and December 1882) concerning Nanny Mattson's engagement to Luth Jaeger; minutes (January 12, 1883) of the Imperial Ice Company, Ltd., of Calcutta, of which Mattson was the chairman; a letter (January 14, 1883) to Luth Jaeger giving Mattson's opinions on the future of Scandinavian language newspapers in the U.S.; and a letter (January 18, 1883) to Mattson from Prince Furrakh Shah. Following Mattson's resignation as Consul General (1883) he became manager of the Maxwell Cattle Company of Cimarron, New Mexico. This company held 1,714,000 acres of grazing, mining, and timber lands in New Mexico and Colorado. There are a few letters with information on the company in the latter part of 1883. Mattson's diary for 1884-1885 (Volume 8) also contains information on the venture.

The remaining correspondence (1884-1939) is not nearly as complete. There are a few letters from Mattson to family members from various places in Europe and the U.S. Some items of interest include a paper, "Our Part in the Reconstruction," written and read by Mattson at the reunion of the 3rd Minnesota Regiment (September 1, 1886); a speech on India (March 1888) and a Decoration Day speech (May 30, 1888), both delivered by Mattson at Clearwater, Minnesota; articles of incorporation and minutes (April 6, 1889-January 12, 1891) of the Scandinavian American Publishing Company of Minneapolis, which published an English-language paper, The North, edited by Luth Jaeger; letters from Alexander Ramsey (January 3, 1892) and President Benjamin Harris (February 15, 1892) on the publication of Mattson's book, Reminiscences: Story of an Immigrant; another letter from Sourindro Tagore (March 12, 1889); memorials to Hans Mattson (1893); and brief biographical data on Hans Mattson's son Edgar (1939).

Correspondence and miscellaneous papers (1987-1990) relate primarily to the following three events honoring Hans Mattson: the dedication of a marker placed in Vasa, Minnesota by the Minnesota Historical Society entitled "Mattson's Settlement" (July 9, 1988); the dedication of a memorial marking Mattson's birthplace in Önnestad, Sweden (August 22, 1988); and the celebration of "Hans Mattson Day" in Minneapolis (October 14, 1990). The papers primarily consist of correspondence related to invitations to these events offered to various state officials, prominent businessmen, academics, and Swedish diplomats.

Newspaper clippings (undated and 1862-1932) include articles dealing with the Civil War; the Maxwell Land Grant Company (1883, in Dutch); East Indian affairs (1882); Jacob Falstrom and the Swedish settlement in Minnesota (1914); and biographical data and obituaries related to various Mattson family members.

Photographs of the Mattson family and scrapbooks (1858-1932), consisting almost entirely of clippings from a variety of English-language and Swedish-language newspapers, most of them relating to Hans Mattson and other family members are also included.

Oversize materials include certificates, documents, maps, and resolutions related to Mattson's service in the Civil War, as Consul General in India, and as Minnesota Secretary of State, as well as his membership in various Swedish fraternal organizations.