The Six Companies, Inc. Hoover Dam Photograph Collection (1931-1935), consists of approximately 400 black-and-white photographic prints contained in two photograph albums and an additional twenty-one loose black-and-white photographic prints with ten corresponding photographic negatives.

The Mike O'Callaghan Professional Papers (1943, 1968-2004) mainly consist of research files gathered by Mike O'Callaghan in his post-political capacity as executive editor of the Las Vegas Sun as well as owner and publisher of the Henderson Home News, Boulder City News, and Green Valley News. The papers also contain handwritten and typewritten drafts of O'Callaghan's "Where I Stand" article for the Las Vegas Sun, along with his reporter's notebooks, monthly planners, and photographic prints. The research files cover a wide variety of topics, including but not limited to environmental issues; nuclear waste; state and local politics; military and veterans affairs; foreign relations including Israel, Iraq, and Korea; and education. The collection also contains copies of speeches given by O'Callaghan as the 23rd Governor of Nevada between 1971 and 1979, some of which contain handwritten notations.