The Howard A. Walsh papers contain diaries, technical papers, and other material related to the life and work of Walsh throughout the first half of the 20th century. The collection's six diaries cover the years 1925, 1926, 1928, 1929, 1930, and 1931, and primarily consist of brief daily entries chronicling Walsh's work for the Doble Engineering Company. As a knowledgeable engineer, he toured the country and worked on a number of different systems, and though his diaries primarily record his professional exploits, they also contain some personal comments. Several entries throughout October 1929, for example, chart his mounting financial losses during the stock market crash, which eventually amounted to at least $2,000.
An engineering notebook contains photographs and colored illustrations of 1920s-era electric transformers and other related equipment, as well as notes about their operation and technical specifications. A series of technical papers and memos complete his professional papers, and provide a picture of the industry in the mid-20th century. Other material in the collection includes a series of photographs and ephemera related to cars, motorcycles, and boats owned by Walsh throughout his life, as well as a draft of his autobiography about his experiences during World War I.