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Technical Information

National Digital Newspaper Program (NDNP)

Copy reader sending dispatches on a telegraph machine
News room of the New York Times newspaper, 1942.

The digitized newspapers available in Chronicling America are produced through the National Digital Newspaper Program (NDNP), a partnership between the National Endowment for the Humanities (NEH) and the Library of Congress (LC). NDNP is a long-term effort to provide permanent access to a national digital resource of historic newspapers, selected and digitized by NEH-funded institutions (awardees) from all U.S. states and territories. This program builds on the legacy of the strategically successful United States Newspaper Program (USNP, 1982-2011), a project sponsored by the NEH with technical support from LC which organized the inventory, cataloging, and selective preservation on microfilm of a corpus of at-risk newspaper materials.

As part of the NDNP digitization process, awardees adhere to technical specifications posted and updated annually by the Library of Congress.

More information is available from the National Digital Newspaper Program (NDNP) website.

Application Programming Interface (API)

To encourage a wide range of potential uses, we designed several different views of the data we provide, all of which are publicly visible. These interfaces, which are documented in detail at the APIs for site, provide a means to retrieve structured data about Library of Congress collections in popular representations such as JSON and YAML for easy use in software programs and analysis tools. This API is accessible to the public with no API key or authentication required, however, rate limiting is strongly encouraged.

The APIs for site also provides documentation about microservices to allow for more targeted interactions. The Text Services API allows for access to full text, word coordinates and context snippets. The Image Services API provides access to images from the Library of Congress using the International Image Interoperability Framework (IIIF) Image API.

Optical Character Recognition (OCR)

What is OCR?

Person laying out page of newspaper.
Composing room of the New York Times newspaper. Making up the sport page, 1942.

Optical character recognition (OCR) is a fully automated process that converts the visual image of numbers and letters into computer-readable numbers and letters. Computer software can then search the OCR-generated text for words, phrases, numbers, or other characters. However, OCR is not 100 percent accurate, and, particularly if the original item has extraneous markings on the page, unusual text styles, or very small fonts, the searchable text OCR generates will contain errors that cannot be corrected by automated means.

Although errors in the process are unavoidable, OCR is still a powerful tool for making text-based items accessible to searching. For example, important concept words often appear more than once within an article. Therefore, if OCR misreads one instance of a key word in a passage, but correctly reads the second instance, the passage will still be found in a full-text search.

Bulk OCR Downloads

To enable research and external services Chronicling America provides bulk access to its OCR data. Please visit the Chronicling America Datasets page for more information.

Chronicling America and the Directory of U.S. Newspapers in American Libraries

The Directory of U.S. Newspapers in American Libraries (previously known as the United States Newspaper Directory and included in the Chronicling America: Historic American Newspaper online collection until 2023) is a separate collection hosted at the Library of Congress derived from the library catalog records primarily created by state institutions during the United States Newspaper Program, 1982-2011. All newspaper titles included in the Chronicling America collection are cataloged and described to Cooperative ONline SERials Program (CONSER) standards and included in the Directory of U.S. Newspapers in American Libraries. For additional information, please visit Directory of U.S. Newspapers in American Libraries: A Guide for Researchers.

Supplemental Description (Newspaper Title Essays)

Person typing on a linotype machine.
Composing room of the New York Times newspaper. Linotyper's hands, 1942.

In addition to standardized description based on existing cataloging records, newspapers that have been selected for digitization by NDNP state partners are accompanied by supplementary description (also known as “title essays”). These essays contain basic information about the paper, including:

  • place of publication (if not already evident);
  • dates and schedule of publication (e.g., weekly, daily, morning, or evening);
  • geographic area covered and circulation statistics;
  • political, religious, or other affiliation and reason for publication;
  • specialized audiences;
  • physical attributes;
  • changes in name, format, and ownership.

In addition, title essays usually discuss:

  • editors, publishers, or reporters of note;
  • significant events covered by the paper in the relevant time period (a short quote from the paper itself can help provide a sense of the paper's voice);
  • special features such as poetry or fiction, women’s section, sports, society, etc.;
  • relationships with other area newspapers;
  • innovations or advances in newspaper production and technology.

These brief essays appear as part of the descriptive title information. NDNP state partners research and write these essays specifically for Chronicling America. The Division of Preservation and Access of the National Endowment of the Humanities review the essays as part of the NDNP partnership. The essays are intended as starting points for additional research and understanding of the historical role of each newspaper.

Newspapers that have title essays are identified in the "Essay Available" column of the “All Digitized Titles” list. The content of the essays can be searched through the Directory of US Newspapers in American Libraries search form, using the Advanced Search “keyword” search. Results will link to records that include those keywords.

Historical newspapers reflect the language and attitudes of their time, and may contain biased, offensive, and outdated words and images that may be hurtful to particular groups or people. In the title essays, writers strive to avoid this language in supplemental text and only include these terms where it is deemed necessary to understanding the context in which the newspaper was produced. Title essay authors only use such language in the title of the newspaper, the name of an affiliated organization, part of the self-identification of a person or group, or if we are directly quoting from the newspaper. Even then, the title essays only include these terms if the author deems it necessary to understanding the context in which the newspaper was produced.

Link to Chronicling America Resources

Man selling newspapers from a horse-drawn cart.
Newspaper vendor and cart in camp, 1863.

The Chronicling America collection uses links that follow a straightforward pattern. You can use this pattern to construct links into specific newspaper titles, to any of its available issues and their editions, and even to specific pages. These links can be readily bookmarked and shared on other sites. The link pattern uses LCCNs, dates, issue / edition numbers, and page sequence numbers.



Automatically generated citations in three styles are provided on every title, issue, and page view of the collection under the "Cite This Item" feature. Citations are generated automatically from bibliographic data as a convenience, and may not be complete or accurate. When describing Chronicling America as the source of content, please use the URL and a web site citation, such as "from the Library of Congress, Chronicling America: Historic American Newspapers site". Consult Rights and Access for more information.

Contacts and More Info

Boy selling newspapers on the street.
Newsboy from Alaska, between 1909 and 1920.

There are many ways to stay in touch or ask questions related to Chronicling America and the National Digital Newspaper Program (NDNP).