- Census records from Nicollet County from 1860-1920, including the state census records from 1865, 1875, 1885, 1895, and 1905, as well as the 1857 census and the 1890 Civil War Veterans census, which can be used as a substitute for the destroyed 1890 federal census.
- Surname and subject files of published items from newspapers and other sources.
- Maps, atlases, and plat books that list rural land owners and show the sizes and locations of their properties. Years available include 1885, 1899, 1913, 1927 and a number of additional years beyond.
- City directories or telephone books, mainly from St. Peter and North Mankato. For St. Peter, the following years: 1899, 1919, 1922, 1923, 1926, 1929, 1931, 1933, 1934, 1939, 1945, and the years thereafter. For North Mankato, Polk city directories for the following years: 1938, 1945, 1948, 1953, 1957 and thereafter. Rural listings for portions of Nicollet County included in the various directories as well.
- Microfilmed newspapers from Nicollet County. The collection mainly consists of the following items: St. Peter Herald, 1884-2004; complete collection of St. Peter Tribune; Nicollet, 1896-1982; North Mankato, 1935-1946; Lafayette, 1956-1982. Information from issues not available on microfilm may possibly be included in clippings found in the file cabinets containing “Subject Files” or “Surname Files.”
- Cemetery records from all of the cemeteries in Nicollet County. Records from Woodlawn Cemetery in Le Sueur county are included. These records begin with the earliest records and continue into the early 1980s. Obituaries contained in the “Surname Files” can be used to supplement the information found in the cemetery record listings.
- Church records in booklet form or on microfilm. These vary widely in their degrees of usefulness. While some contain records of births, marriages, deaths, and confirmations, others focus mainly on details about the clergy and the church buildings.
- Numerous histories and reference books about Nicollet County and Minnesota, such as Gresham’s “History of Nicollet and Le Sueur Counties,” Neill’s “History of the Minnesota Valley,” and Hughes’ “Old Traverse des Sioux.” Each is well indexed in order to facilitate surname searches..
- Copies of the St. Peter Herald’s “Diamond Jubilee” issue from 1930 and the St. Peter Herald’s 1985 ‘Centennial” issue, both of which contain detailed histories of St. Peter. Both issues are indexed by surname and by subject.
- A large collection of “Minnesota History” magazine and two of its index volumes that are extremely well indexed by surname or topic.
- A large collection of photographs of people who lived in Nicollet County. The photograph collection also contains many images of buildings and places in Nicollet County, including some photographs of old houses.
- A large collection of manuscripts, many of which contain useful family history information.
- Numerous donated family histories.
- St. Peter High School yearbooks, beginning with the year 1949.
- Gustavus Adolphus College yearbooks, an assortment that begins with the 1924-1925 issue.
- A variety of other items are available at the Nicollet County Historical Society that may be used by researchers. Researchers should ask a staff member in the archives for help locating additional items.