Frank J. Sprague

Frank Julian Sprague (July 25, 1857 – October 25, 1934) was an American inventor who contributed to the development of the electric motor, electric railways, and electric elevators. His contributions were especially important in promoting urban development by increasing the size cities could reasonably attain (through better transportation) and by allowing greater concentration of business in commercial sections (through the use of electric elevators in skyscrapers). He became known as the "father of electric traction". Demonstrating an aptitude for science and mathematics, Sprague secured an appointment to the U.S. Naval Academy in 1874 and, after graduation in 1878 and 2 years at sea, resigned to pursue his career in electrical engineering.

Sprague was born in Milford, Connecticut, in 1857 to David Cummings Sprague and Frances Julia King Sprague, a school teacher. His mother died when he was ten, and he was sent by his father to live with an aunt in New York. He attended Drury High School in North Adams, Massachusetts, and excelled in mathematics. After graduating high school, Sprague went to Springfield, Massachusetts, to take an entrance exam for West Point, but somehow unexpectedly was taking the four-day entrance exam for the United States Naval Academy in Annapolis, Maryland. He got the highest score (twelve others took the exam), and to go to the school, he needed to borrow money. A local contractor and a bank loaned him four thousand dollars, and he travelled to Maryland. There, he graduated seventh (out of thirty-six) in the class of 1878.

He was commissioned as an ensign in the United States Navy. During his ensuing naval service, he first served on the USS Richmond, then the USS Minnesota. While in Asia, Sprague wrote stories he filed for the Boston Herald. While his ship was in Newport, Rhode Island, in 1881, Sprague invented the inverted type of dynamo. After he was transferred to the USS Lancaster, the flagship of the European Squadron, he installed the first electric call-bell system on a United States Navy ship. Sprague took leave to attend the International Exposition of Electricity of 1881 in Paris and the Crystal Palace Exhibition in Sydenham, England, in 1882, where he was on the jury of awards for gas engines, dynamos, and lamps.

In 1883, Edward H. Johnson, a business associate of Thomas Edison, persuaded Sprague to resign his naval commission to work for Edison. Sprague, who began at a salary of $2,500, was neither happy with his salary nor his assignments. Sprague wanted to focus on motors, while motors bored Edison, who was consumed by making his incandescent lighting work. Edison sent Sprague to run the construction departments where Edison had built central power stations for his lighting systems in Sunbury, Pennsylvania, and Brockton, Massachusetts.

Sprague did important work for Edison, including correcting Edison's system of mains and feeders for central station distribution.

In 1884, he decided his interests in the exploitation of electricity lay elsewhere, and he left Edison to found the Sprague Electric Railway & Motor Company.

By 1886, Sprague's company had introduced two important inventions: a constant-speed, non-sparking motor with fixed brushes, and regenerative braking, a method of braking that uses the drive motor to return power to the main supply system. His motor was the first to maintain constant speed under varying load. It was immediately popular and was endorsed by Edison as the only practical electric motor available. His regenerative braking system was important in the development of the electric train and the electric elevator.

Sprague's developments in electric traction let cities grow larger, while his development of the elevator permitted greater concentration in their commercial sections and increased the profitability of commercial buildings. Sprague's inventions made modern light rail and rapid transit systems possible, which today still function on the same principles.

The iconic Sprague-Thomson rolling stock of the Paris Métro, in service from 1908 to 1983, are still referred to as les rames Sprague ("Sprague trainsets") today.

Sprague's engines were used as far afield as Sydney Harbour in Australia. A five-horsepower Lundell electric motor used at the Cockatoo Island Dockyard between 1900 and 1980 is now in the collection of the National Museum of Australia in Canberra.

Sprague was awarded the gold medal In Paris at the International Exposition of Electricity in 1889, the grand prize at the Louisiana Purchase Exposition in 1904, the Elliott Cresson Medal in 1904, and the Edison Medal of the American Institute of Electrical Engineers (now Institute of Electrical and Electronics Engineers), for "meritorious achievement in electrical science, engineering and arts as exemplified in his contributions thereto" in 1910.

In addition, he received the Franklin Medal in 1921 and was posthumously awarded the John Fritz Gold Medal in 1935.

Sprague was twice married, first to a Mary Keatinge, and thereafter to Harriet Chapman Jones. Frank and Mary had one son, Frank Desmond. Frank and Harriet had two sons and a daughter: Robert C. Sprague (also an inventor), Julian K. and Frances A. Remembering his father, Robert wrote in 1935:All through his life and up to his last day, Frank Sprague had a prodigious capacity for work ... And once having made up his mind on a new invention or a new line of work, he was tireless and always striving for improvement. He had a brilliantly alert mind and was impatient of any half-way compromise. His interest in his work never ceased; only a few hours before the end, he asked to have a newly designed model of his latest invention brought to his bedside.

Sprague died on October 25, 1934. He was buried with full U.S. Navy honors at Arlington National Cemetery in Virginia. His wife Harriet was interred with him after her death in 1969. After Sprague's death, Harriet turned over a substantial amount of material from his collection to the New York Public Library, where it remains today accessible to the public via the rare books division. Other papers, including six volumes of congratulatory letters and photographs presented to Sprague on the occasion of his 75th birthday, are held at the Chapin Library, Williams College.

In 1999, grandsons, John L. Sprague and Peter Sprague cut the ribbon and started an 1884 Sprague motor at a new exhibit at the Shore Line Trolley Museum, where a permanent exhibit, "Frank J. Sprague: Inventor, Scientist, Engineer", tells the story of the role of the "father of electric traction" and the role of electricity in the growth of cities.

In 2012, the Pennsylvania Trolley Museum adopted a stray cat, naming it after Sprague: Frank the Trolley Cat.

In 2017, Sprague was the subject of an episode on season 29 of American Experience, a documentary series that was broadcast on PBS television stations. Titled The Race Underground, it partly chronicled the beginnings of the Boston-area MBTA's streetcar network, and described Sprague as "The Forgotten Hero of the American Subway".