This series describes Sperry's inventions and entrepeneurial activities in the two decades (1880-1900) when he was considered one of America's electrical pioneers. It documents his efforts to develop arc lighting systems, stationary power, mining machinery, and electric traction. The records describe the operation of the Sperry Electric Light, Motor, and Car Brake Company, which was founded in 1883 to set up electric power stations and manufacture component parts. These are fragmentary, but they do contain copies of Sperry's agreements with his financial backers and correspondence that traces his efforts to patent his inventions and secure customers.

Records documenting Sperry's associations with the Electric Mining Machine Company and Independent Electric Company are far more complete. These files, which include incoming correspondence, letter books, sales books, and account books, trace Sperry's efforts to develop electric mine cars and undercuttting equipment. Sperry's letter books contain copies of a large number of reports he sent to the engineers at General Electric for analysis and comment. These letters show that Sperry was able to draw on the expertise of many of GE's young engineers who were, during the 1890s, graduating from engineering schools in relatively large numbers. These young engineers helped orient Sperry to the early twentieth-century world of professional engineering.

The Chicago-Cleveland records document Sperry's relationship with the Link-Belt Company, which rented him space to manufacture his electric mine cars. The records also show that Link-Belt provided his company with both technical support and legal advice when he became embroiled in a number of patent infringement suits during the mid-1890s.

The correspondence of the Goodman Manufacturing Company traces Sperry's continued involvement with coal-mining machine industry through the 1920s. These records show that Sperry continued to help make policy decisions and served as a consulting engineer long after he left Chicago.

During the late 1890s, Sperry's primary interest was in street railways. His correspondence from this period describes his effort to develop and patent his electric governor and car brake. Correspondence with GE engineers show that Sperry's street car employed a mode of power transmission similar to that in his mine locomotive. The records describe Sperry's efforts to market his street cars as well as his increasing commitment to experimentation and testing. Other records from Sperry's Chicago-Cleveland period include those generated by the Sperry Engineering, National Battery, and Whitley Exerciser Companies.

Taken together, these records suggest that from his earliest days as an electrical engineer, Sperry was experimenting with automatic feedback control. His arc lighting and dynamo patents describe two major improvements: a mechanical governor to automatically maintain uniform output, and an electromagnetic control mechanism to adjust current output to reflect load variations. As Thomas Hughes has pointed out, the operation of Sperry's centrifugal governor was very similar to the conventional feedback devices used in steam engines and anticipated his experiments with gyroscopic feedback control.

The papers clearly demonstrate that by the mid-1880s, Sperry was recognized as an important electrical pioneer. He was a founding member of the National Electric Light Association, which was attempting to regulate the high-power lines developed to transmit electricity economically over long distances.