He was born on February 19, 1863 near Northfield, Litchfield County, Connecticut, United States, the son of Horace A. and Charlotte S. (Pierce) Potter. Until he was fourteen he lived on a farm, but was not particularly interested in farming.
In 1877 he went to live in Thomaston, Connecticut, and four years later graduated from the high school.
During vacations in high school he worked in the shops of the Seth Thomas Clock Company. His inventive genius showed a bent toward electric machinery and during his high-school work he built an electrostatic machine, which was used for exhibition and to accompany lectures which he delivered in several schools.
After his graduation, he began service as a machinist apprentice with Sawtelle & Judd of Hartford, Connecticut. This firm undertook machine repairs and construction of all kinds. A portion of its work was the machining of parts of dynamos for the Schuyler Electric Company. After four years' apprenticeship he served two years as a journeyman machinist with the same firm, one of his duties being to take care of the engines of the Hartford Electric Light Company. The electrical business was then in its infancy, and foreseeing a large increase in the supply of electric power, Potter decided to secure a better knowledge of electric lighting and apparatus.
In June 1887, therefore, he entered the employ of the Thomson-Houston Company, Lynn, Massachussets, as machinist on electrical equipment. Within a few weeks he was sent out on the road to do repair work and in the fall of 1887 went to Durham, North Carolina, where arc-lighting equipment was being installed.
At the request of the Thomson-Houston Company, he then became superintendent of the Electric Lighting Company at Raleigh, North Carolina, which was afterwards merged into the Raleigh Gas Company, and spent some months overhauling the existing distribution system and erecting lines for city lighting. About this time he became interested in the construction of electric railways and, deciding to enter this field, he returned to Lynn in 1889.
Three months later, he was sent to install equipment for the West End Railway in Boston, which was just then initiating electric traction. Other construction work carried him to Albany, Utica, and Saratoga. He was then sent to San Antonio, Texas, where a contract had been made for the installation of five miles of electric railway within forty days. Working with the associate civil engineer, he was able to have the entire equipment, including tracks, overhead, and installation of power completed and the road placed in operation in thirty-eight days.
Upon return to the Lynn works in 1890, he was assigned to the engineering department, because of his extensive experience in the building of machines and handling outside construction work. In connection with a study of electric railway equipment in 1892, Potter, in collaboration with Walter H. Knight, devised the series-parallel controller. About this time the organization of the General Electric Company took place, and the Thomson-Houston Company was absorbed. The railway engineering work was transferred to Schenectady in 1894 and Potter there continued his work on the development of electric railway apparatus. In 1895 he was appointed chief engineer of the railway department.
During the World's Columbian Exposition at Chicago in 1893 he had entire supervision of the General Electric Company's exhibit and was especially active in taking care of the power equipment. At this time he designed the necessary panels for controlling the power station equipment and later developed a full line of railway switchboards. During one of his foreign trips he gave considerable attention to the London underground railways, which were just then being put into service. The work on the Butte, Anaconda & Pacific, the Chicago, Milwaukee & St. Paul, and the Victorian railroads was carried out under his general supervision.
Early in 1921 he went abroad and spent several months studying conditions in France, Italy, Switzerland, Great Britain, and Spain. His later work included the development of a special high-capacity overhead line construction and the otheograph for recording the wheel action of various types of rolling stock.
His death, in his seventy-first year, was occasioned by a heart attack.
William Bancroft Potter issued for various inventions more than 130 patents. Among the most important of these were the series-parallel controller, the surface contact system, the three-wire system of railway operation, the electropneumatic contact, and the otheograph. Among others, were inventions in connection with electric switching, motors, generators, third rail, electric braking, airbrakes and devices for motor control. He started the first electric lighting system in Greensboro. As the chief engineer of the railway department of General Electric Company he devoted considerable time to marine apparatus and electrical combustion engines. He was also active in the installation of equipment for the Manhattan Elevated Railway in New York. Other large projects with which he was connected were the electrification of the Baltimore & Ohio and the Paris-Orleans railroads, the New York Central Terminal, the West Jersey & Sea Shore Railroad, the Detroit tunnel, and the Great Northern and Southern Pacific lines.
He was twice married: first, July 3, 1890, to Loretta Harward of Raleigh, North Carolina; second, September 23, 1912, to Rose Hubbard, of Sandusky, Ohio. He had one son, Harward, and a daughter, Dorothy.
