By Rose Buchanan, Archivist and Subject Matter Expert for Native American Related Records

As the National Archives continues to digitize our microfilm collection, more records related to Native Americans are becoming available online in the National Archives Catalog. This includes microfilmed indexes and registers for a key series of correspondence: the letters received by the Office of Indian Affairs (OIA) central office for the period 1881–1907 (Entry PI-163 91; National Archives Identifier 300337), commonly called the “Entry 91 letters.”

What are the Entry 91 letters?

Like today’s Bureau of Indian Affairs (BIA), the OIA in the nineteenth century had a central office in Washington, DC, and multiple field offices around the country. After OIA superintendencies were discontinued in the 1870s, OIA agents in the field wrote directly to the central office to report on activities and issues within their jurisdictions. The OIA central office also regularly received letters from other government departments (such as the War Department and the Treasury Department) and from Congress, state and local government officials, businesses, Tribal members and representatives, and members of the public.

These letters covered a wide range of topics related to Native Americans, including:

  • Education
  • Health
  • Population
  • Subsistence
  • Annuity payments
  • Land allotments
  • Rights-of-way
  • Resource use
  • Inheritance and heirship
  • Federal Indian policy

The broad subject coverage makes this series one of the most useful for researching OIA activities during the 1881–1907 period.

How are the Entry 91 letters arranged? What information do I need to access them?

The Entry 91 letters are arranged by year and thereunder by file number. Thus, to access the Entry 91 letters on-site or request copies off-site, researchers need to know the year and file number for each letter of interest. This information can be obtained from indexes and registers (discussed in more detail below).

File numbers begin with 1 for each new year. The OIA central office assigned file numbers in the order in which they received the letters, not based on letters’ content.

An example is seen in File 1888-1014. This file discusses conditions at the Native American boarding schools in Carlisle, Pennsylvania, and Hampton, Virginia, as determined by Reverend T. S. Childs, who was appointed by the Secretary of the Interior to conduct a special investigation of the schools. Dated January 11, 1888, Childs’s report was the 1014th letter that the OIA central office received in 1888. The year and file number are indicated in the stamp at the top of the letter wrapper (the document surrounding a letter and its enclosures). Most Entry 91 letters include letter wrappers with such stamps, which also provide the date that the OIA central office received the letter (in this case, January 12, 1888).

In this example, the year and file number are also included in a handwritten note at the bottom of the letter wrapper, although the file number is listed first, followed by an abbreviated form of the year. A stamp with the year and file number appears on the back of the actual letter (and related enclosures) as well.

Excerpts from File 1888-1014. Stamps on letter wrappers and letters themselves can provide the year and file number needed to request Entry 91 letters.

Are the Entry 91 letters microfilmed or digitized?

No, the Entry 91 letters are not microfilmed or digitized; they currently exist only as textual records housed at the National Archives in Washington, DC.

However, indexes and registers to these letters are digitized and available in the National Archives Catalog. Prior to digitization, the indexes were available as NARA Microfilm Publication P2187, while the registers were available as NARA Microfilm Publication P2186.

How do I use the digitized indexes and registers to find Entry 91 letters?

If you are looking for a letter related to a particular person, place, or topic, it is most helpful to start with the indexes to the Entry 91 letters (National Archives Identifier 2106003). The indexes are arranged in five chronological time periods: 1881–1886, 1887–1892, 1893–1899, 1900–1906, and 1907. Within each period, the entries are arranged by subject in rough alphabetical order. Entries related to OIA agencies and schools are often listed separately and subdivided into subjects arranged in alphabetical order. Each entry in the index provides the years and file numbers of relevant letters.

For example, if you were searching for Rev. Childs’s 1888 report about conditions at Carlisle and Hampton, you could check the indexes covering 1887–1892 and subjects A–C. Browsing the entries for “Childs,” you would eventually find Image 164 of 282 (page 491 of the index); Rev. Childs is the fourth entry under “Child(s).”

T. S. Childs's entry in the index

Childs’s entry lists multiple years and file numbers. Note that each year within this portion of the index (i.e., 1887–1892) is listed separately, followed by the string of file numbers associated with Childs during that year. File numbers are separated by periods and are listed in numerical order for each year. You can see that 1014 is among the files listed in Childs’s entry for 1888.

Close-up of T. S. Childs's entry in the index

This information—the year and the file number—would be enough to pull the file on-site or request a copy remotely. However, if you did not already know that File 1888-1014 relates to Childs’s 1888 investigation of the Carlisle and Hampton schools, you would want to confirm that the file relates to this topic first.

You could check the registers for the Entry 91 letters (National Archives Identifier 2106070) to confirm. The registers provide the name and address of the letter writer, the date the letter was written, the date the letter was received by the OIA central office, a brief overview of the letter’s subject matter, and the file number. If the OIA central office answered the letter, the date of the response is also usually included. Within each register, letters are listed in the order the OIA central office received them, meaning that they are typically listed in order by file number.

To determine the subject matter of File 1888-1014, you could browse the registers covering January 3, 1888–March 20, 1888 until you saw the entry for File 1014. Information in the registers is organized into columns, with the date that the OIA central office received the letters listed at the top of each page. File numbers appear in the leftmost column, so you could browse the pages until you saw “1014.” If you reached the end of the register and it did not include File 1888-1014, you could go to the next register for 1888, and it would pick up where the previous register left off.

However, the entry for File 1888-1014 does appear in the registers covering January 3, 1888–March 20, 1888, specifically in Image 56 of 405 (page 105 of the register). The file number (1014) appears in the leftmost column, followed by Childs’s name, the date of his letter (January 11), and a brief description of the letter’s contents: “Report of investigation of Hampton and Carlisle Schools.” Now you know that File 1888-1014 relates to your topic.

T. S. Childs's entry in the registersClose-up of T. S. Childs's entry in the registers

What if I am interested in letters received from an OIA agency or school?

You can check the indexes under the name of the agency or school. Agencies and larger schools typically have several pages in the indexes devoted just to them. These pages are often included at the back of the indexes after the main entries for individuals and other subjects—although not always; sometimes the entries for agencies and schools appear within the main list of entries in the appropriate place alphabetically. Within an agency’s or school’s index pages, entries are divided into categories such as “Annual reports,” “Buildings,” “Employees,” etc.

For example, if you wanted to find other letters received by the OIA central office in 1888 related to the Carlisle Indian Industrial School, you could again check the indexes covering 1887–1892 and subjects A–C, but this time under “Carlisle School.” You would find that the entries for Carlisle begin with Image 213 of 282 (page 589 of the index) and continue to Image 221 of 282 (page 604 of the index).

Often, only the first page relating to an agency or school lists the agency’s or school’s name; this information usually appears on a tab along the right-hand side of the index page. Thus, to ensure that you do not miss entries for an agency or school, it is important to browse the indexes until you see a tab for a new agency or school.

Carlisle School page in the indexes

Not all schools for Native Americans will have separate index pages. Some smaller schools, especially those operated by private groups, will be incorporated into the main set of index pages for the relevant time period. Cross-references to these smaller schools are sometimes included in different parts of the index, if the schools went by multiple names.

For example, the privately-run Martinsburg Indian Boarding School in Martinsburg, Pennsylvania, is listed under “M” in the 1887–1892 indexes for subjects M–P (see Image 16 of 316; page 26 of the index). Rather than listing years and file numbers, however, the entry says “See Junieta Collegiate Institute.” Checking under “J” in the 1887–1892 indexes for subjects H–L leads to an entry for “Juniata Collegiate Institute, Martinsburg, Pa” (see Image 122 of 226; page 273 of the index). This entry includes dozens of references to file numbers, which you could cross-reference with the registers to determine their specific subject matter.

Martinsburg Indian Boarding School index entryJuniata Collegiate Institute index entry

Are the indexes and registers to the Entry 91 letters searchable by keyword?

Yes, you can search the indexes and registers by keyword. To do this, click the “Search within this series” link on the indexes’ and registers’ Catalog pages.

Search within a series button in the National Archives Catalog

However, keyword searches are not 100% accurate because they are based on optical character recognition (OCR) and artificial intelligence/machine learning. These technologies do not always transcribe handwritten text or non-English names accurately.

Can I help transcribe the indexes and registers to the Entry 91 letters to improve keyword searches?

Yes! The National Archives Catalog includes a transcription tool, which you can use to help improve the accuracy of keyword searches for everyone. You will first need to register for a free Catalog user account. See Get Started Transcribing for more information.

Who should I contact if I have more questions about the Entry 91 letters, indexes, or registers?

Please contact the Archives 1 Textual Reference Branch at

Does the National Archives house other OIA correspondence?

Yes! Several examples are listed below. These examples are all digitized and available in the National Archives Catalog.

  • NARA Microfilm Publication M271, Letters Received by the Office of the Secretary of War Relating to Indian Affairs, 1800–1823 (National Archives Identifier 1991067)
  • NARA Microfilm Publication M15, Letters Sent by the Office of the Secretary of War Relating to Indian Affairs, 1800–1823 (National Archives Identifier 2007294)
  • NARA Microfilm Publication M234, Letters Received by the Office of Indian Affairs, 1824–1880 (National Archives Identifier 300331)
  • NARA Microfilm Publication M21, Letters Sent by the Office of Indian Affairs, 1824–1881 (National Archives Identifier 2105779)

If you have additional questions about OIA correspondence, please contact us.