The Hattie M. and Merritt Morse papers document the experience of a 19th-century New Hampshire family during the American Civil War. Hattie was married to Merritt Morse, a Union serviceman stationed in South Carolina, the Sea Islands, and Virginia. These papers contain correspondence received by Hattie and artifacts from Merritt's service: carte de visite photographs, a leather wallet with a Confederate ten-dollar bill, and a pair of Lemaire field glasses.

The bulk of the correspondence is from Merritt, while serving in the war, home to Hattie, living with their parents and young son in New Hampshire. A small amount of earlier correspondence to Hattie from members of her family documents the shift in family life after her father’s death which results in her mother joining her household. Family letters written to Hattie during the war share concern for Merritt's safety as well as details of social and religious life at home. Merritt’s letters, running from 1863-1865, detail his experiences serving in the New Hampshire 3rd Infantry, the U.S. Signal Corps, the X Corps Army of the James in Virginia, and the XXIV Corps in Virginia.

Merritt describes his observations and interactions with members of the formerly enslaved Black communities on the mid-Atlantic Sea Islands, in particular the Gullah community, through his unofficial work as a minister. He comments on the Black community and culture, a celebration of the Emancipation Proclamation, race relations, conditions under slavery, and includes the names of the formerly enslaved in connection to their enslavers. He also offers his opinion of white Northern teachers and missionaries sent to the Sea Islands as part of the Port Royal Experiment.

Additionally Merritt discusses the Army efforts to establish the signal system across islands still under Confederate control. Letters from his service in the X and XXIV Corps give accounts of the Battle of Pocotaligo, the Battle of Fort Wagner, the Siege of Charleston Harbor, the Bermuda Hundred Campaign, the Richmond-Petersburg Campaign, and the surrender of General Lee at Appomattox. He witnesses conscription of freedmen by Union soldiers from African American regiments and the discrimination that these soldiers faced from their white counterparts. Merritt also describes medical conditions in the army hospital where he was a patient and ward master in 1864, leading to his acquaintance with the nurse Clara Barton.

Photographs are all carte de visite style portraits of soldiers, mostly pictured in uniform, that Merritt met during his service. Many are signed by the subject, and many also include a backstamp with the photographer's name and studio location. The bulk were either shot in New Hampshire or at the 24th Army Corps headquarters.