This collection contains two subgroups: Walter Washington De Lacy and the De Lacy Family. The Walter Washington De Lacy subgroup consists of outgoing correspondence to family in New Orleans. The majority of the letters are typed copies to his cousin, Fannie S. De Lacy, and his uncle, Walter De Lacy. The letters discuss family matters, professional activities, and Helena and Montana conditions. Outgoing correspondence of Fannie, William, and Zelene de Lacy, Walter W. De Lacy's cousins.