Frank J Sprague had an on again, off again relationship with Thomas Edison. A graduate of the US Naval Academy, Sprague developed electric dynamos and electronic communication systems for US Navy ships. In 1883 and 1884 he worked at Menlo Park, where he invented the electric traction motor. Between 1885 and 1890, Frank J Sprague owned the Sprague Electric Railway & Motor Company. They won contracts to build ten different street car systems in the USA. In 1890, he sold out to Edison and his business partners. He went back to Menlo Park and worked on developing electric elevators and a multiple unit control system for electric railways. In 1892 Sprague quit Edison and formed the Sprague Electric Elevator Company, but sold it to the Otis Elevator company in 1895. After that, he went back to Edison's fairly new General Electric Company and moved to Schenectady NY where the General Electric company based their Electric Railroad operations. Sprague continued to work for General Electric until 1917 on a variety of railroad electrification projects.
Sources: "The Interurban age" and "When Steam Railroads Electrified", both books were written by William Middleton

If you dig into the digital edition at the Edison Project site, you can actually specify payroll records, patents, and anything else you want, and find the names on original documents.

Tesla, by the way, was never "part of the stable of inventors and engineers at Menlo Park." He worked for the European company, then transferred to the machine works in NY, and left there shortly after. The permutations of the various Edison companies and operations are themselves hard to follow sometimes, but Lewis Latimer and Sprague (whom /u/davratta points to rightly as a major force among the engineers) were important in the electric light system. John Kruesi is another involved in the rollout of illumination plants in the early 1880s. William J. Jenks also did some work on the development of the 3-wire system. But the phonographic, food preservation, ore-separation/mining, cinematic, cement, and other ventures had different key players, and the field was pretty vast. Some who were managers later did work on these projects, like Charles Batchelor. But again, people involved in the EEC and Illuminating Company weren't part of the early consortium of inventors, and later groups were in other places, not in Menlo Park.

I'd like to recommend this site which gives a pretty good overview of the history of and key players in the 'age of electricity'. (and dispels some myths about Tesla, who - as Edison as well - often gets undue credit for inventing many things others had either invented or substantially contributed to).

davratta wrote about Sprague, who's mentioned there too, to add another I'd William Stanley, who started out working with Westinghouse but later worked for Edison. Stanley did a lot of pioneering work with AC transformers (although to say that he, or any single individual 'invented' it would be a distortion, same goes for many things at that time - electricity was a hot topic!). In 1886, in Great Barrington, Mass., he built the first commercial AC production-distribution systems in the USA. (one of those things Tesla often gets credited with).