This series includes Solon Borglum's incoming and outgoing professional correspondence. Materials dated after 1922 are Monica Borglum Davies' incoming correspondence regarding Solon's artwork and legacy. Solon's correspondence is with galleries and foundries, such as the Milch Gallery and Roman Bronze Works, concerning the sale or production of his artwork, and correspondence with people and organizations, such as Jane Wallace and Saint Mark's in-the-Bouwerie, concerning sculpture projects, and with other artists, including August Saint-Gaudens and Robert Fulton Logan. Also found is correspondence concerning the School of American Sculpture, both before and after Solon's death.

Materials addressed to Monica Borglum include letters from art galleries and museums, such as the Detroit Institute of Art, the Joslyn Art Museum, and the National Collection of Fine Arts at the Smithsonian Institution, concerning the sale or exhibition of Solon's artwork. Also included is correspondence with foundries concerning the production of Solon's sculptures, and with historical societies, individuals, and other organizations concerning the provenance, collection, or exhibition of his artwork. This series also includes correspondence from the Solon Borglum Memorial Fund and condolences to Monica on the deaths of Solon and Emma (in 1934).

Also found are calling cards, business cards, and envelopes that have been separated from their contents. This series also includes numerous notepads containing drafts of Solon's outgoing correspondence as well as drafts on loose pages.