The Lanphear Family Letters, 1854-1872, consists of four series. The first, entitled Series I. Ruebn Lanphear, contains ten items from Ruebn to his daughter, Eliza, and his sister and brother. These letters span the entire length of the war, from 1861-1865. Most concern Ruebn's struggle with illness and his effort to obtain a military discharge. He also writes of camp life and of the Indian problems of Minnesota.

The second series, Series II. George Lanphear, consists of 24 items from George to family members, primarily his sister, Eliza. Spanning a two-year period from 1861-1863, these letters concern camp life in the 2nd Minnesota Infantry Regiment. Family matters such as his mother and his brother Nelson's death are also discussed. George also describes his regiment's many travels across Tennessee, paying attention to the land and the climate.

Ten items from Mary Cummings to family members, primarily her sister Eliza, can be found in Series III. Mary A. Cummings . The letters describe Mary's and her husband's time at the hospital in Baltimore. She writes to her father asking him to leave Minnesota and live with her in Baltimore. Additionally, Mary discusses the deaths of her brothers Nelson and George.

The final series, Series IV. Other Family Members, contains three items that are from other members of the Lanphear Family. These items, which date from the 1850s through 1870s, describe the move westward, describing the prosperity to be found on the frontier.