Thanks for posting on History Hub
The following is from the Library of Congress Chronicling America newspapers
that maybe helpful in your search.
Dear Ms. Dunn,
Thank you for posting your request on History Hub!
Because the National Archives is primarily a repository of the records of the federal government, we have limited information about local history except as it relates to the activities of federal agencies. If there is a specific aspect of local history you wish to research that has a federal connection, such as the names of postmasters or the military service record of a specific local individual who served in the military, please post a follow-up request on History Hub or submit it privately using NARA’s Contact Form.
We searched the Library of Congress’s Catalog and located several resources relating to Dunbarton, NH and/or Merrimack County, NH. Please use the Library's Ask a Librarian form to submit questions about their holdings.
We also suggest contacting the New Hampshire Division of Archives and Records Management, the New Hampshire State Library, the New England Historical Society, the New Hampshire Historical Society, the Dunbarton Public Library, the Dunbarton Historical Society, and other state and local organizations. You may also wish to reach out to online community forums, such as the Dunbarton Community Group.
For more advice, see the FamilySearch Wiki Page on Merrimack County, New Hampshire Genealogy.
We hope this information is helpful. Best of luck with your research!