The collection consists of 82 letters written by members of the Clark family, primarily Henry, to family members who remained in Independence, Iowa. These letters were written almost exclusively from Montana Territory, starting in Virginia City in 1864 and moving to Helena and other mining camps in 1865. There is much information on these early settlements as well as on economic conditions, the mining and farming methods employed, and Clark's activities in Montana through 1882. Henry's brother, Sanford Clark, died in Iowa in 1878, and the letters thereafter are written to "Sister Delia." In addition, there are four small subgroups containing outgoing correspondence of Clark's wife, Emily; of two of his cousins, Horatio L. Clark and Wells T. Clark; and Cornelius Hedges.