The collection consists primarily of Groot family correspondence. Most of the letters were written by James P. Groot. Notable content includes three letters signed Rachel Mull to her sister Maria—dated September 2, 1855, April 5, 1856, and February 25, no year—that describe the abusive relationship with her husband, Barney Mull. The collection also includes 12 Civil War–era letters signed James P. Groot describing affairs in St. Louis and his military service in the 6th Iowa Infantry.