The William Penn Brooks Papers consists of correspondence, photographs, newspaper clippings, an account book, and translations. The collection is arranged in three series: Correspondence, Biographical and Historical, and Photographs. The majority of letters are from William Brooks to his sister Rebecca Brooks during the period of time when he was teaching in Sapporo, Japan. The time span of the letters range from the late 1800s to the early 1900s, and describe in rich detail life in Japan from the perspective of an American teacher trained in agriculture.

This collection is organized into three series:

• Series 1. Correspondence, 1868-1938
• Series 2. Biographical and Historical, 1878-1939
• Series 3. Photographs, 1881-1887