The Campbell family papers consist primarily of Civil War letters from Alexander and Allen Campbell to their father, John, in Groveland, Michigan. The Campbell brothers joined the 1st Michigan engineers and served for the most part in Tennessee, where they helped build bridges and repair railroads. The letters discuss their experiences and home matters as well as recruitment and opposition to the draft. Their regiment later joined Sherman for his March to the Sea. In one letter Allen describes his part in the burning of Atlanta and the march through Georgia and the Carolinas.

Two other sons of John Campbell fought in the Civil War. George joined the 30th Michigan in early 1865 and was mustered out when the war ended. His brother James also enlisted and was sent to Texas on garrison duty. He remained in the Army through 1866, and letters from his brothers advise him to be patient and get through his service as cheerfully as possible.

Also included in the collection are several letters to John Campbell from business associates in New York. One letter (December 31, 1860) speculates about the possible effects of the Southern States' secession on business. Another, dated December 18, 1861, evaluates the impact of the war thus far and the possibility of British intervention.

Some photocopies have been included in place of original letters.