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Louis Duncan was born in Washington, D.C., on 25 March 1861, most likely at the home of his maternal grandmother, Harriet Bowen Morriss As his parents already had two boys and no girls, they probably were expecting Louis to be a girl. It is believed that he was named Louis Amory after his mother's greatly loved sister Louise Amory Morris Corcoran who died in 1840. When he became a little older, the thought of being after a girl caused him some consternation, and he quickly dropped the Amory, and simply became Louis Duncan. The Civil War was just commencing at this time and his grandmother strongly urged his mother to stay with her in the safety of Washington, but she refused and returned with her babe Louis to Markham Station, Virginia, where Rev. Thomas Duncan had a parish. It was about 45 miles from Washington and sometimes it was in Union hands and sometimes under the Confederates. Here he spent his childhood and received his basic education from his mother. He probably obtained a little formal schooling while they were living in Brookeville, Maryland, and when the family moved to Knoxville, Tennessee, in 1875, he attended the East Tennessee University, Preparatory Department School for a year.

About this time he became interested In attending the Naval Academy and tried to obtain an appointment in Tennessee, but none were available there. He was lucky enough to obtain one in the adjoining state of Kentucky, and took the competitive entrance examinations in early September 1876. He successfully passed, and entered the U.S. Naval Academy at Annapolis, Maryland, on 11 September that same year. He graduated from the Naval Academy 10 June 1880 and was appointed Cadet-Midshipman, U.S.Navy.

In a letter to his mother dated 26 June 1882, he said "If you hear of a chance for a young man with a new mustache and remarkable intellect to make a fortune in a short time telegraph. I feel I'm wasted in the service, nothing to work for. I am not phenomenally smart, but I am a little above the average and would like a chance to study for something." It can be assumed that soon after his arrival in Baltimore, he made inquiries as to possibilities to further his education. On 15 September 1882 he requested nine months. leave of absence, which was granted that same day,and it was during this time that he planned his future career.

On Navy Department orders of 17 April 1883, "Ensign" Louis Duncan was ordered to the Torpedo School at Newport, R.I. He must have received a temporary promotion to Ensign as his permanent Ensign's commission was not effective until 26 June 1884. While at the School he did considerable experimenting with electricity and constructed a machine, as he called it, which in effect was a type of dynamo. This type of work greatly appealed to him. He was detached from the Torpedo, Station 24 July 1883 and granted leave until 10 June 1884. Returning to Baltimore be renewed his contacts with Johns Hopkins University, and actually persuaded the Navy Department to order him to that University for such special duty as the President of the University may assign him. Such duty was to commence 1 December 1883 and continue to 1 December 1884.. The President assigned him to Professor Rowland for further instructions. On 30 November 1884 he received orders to remain on shore duty until 1 July 1885. On 11 June 1885 the Degree of Doctor of philosophy was conferred on him by Johns Hopkins University. Subject: Physics and Mathematics. Thesis: On the Determination of the Ohm by the Lorenz Method. He determined the unit of electrical resistance for the U.S. Government, which was established as 106.30 centimeters of mercury of one millimeter cross section.

On 2 March he heard that Pr. Rowland will offer him the charge of a new Electric Laboratory at Johns Hopkins University. Shortly afterward he went to the University in regard to that position, and being appointed. an Associate in Physics. He was successful in both, his appointment as Associate being for three years commencing10 September 1886, at a salary of $1500 per year. The thought of leaving the Navy made him quite blue, but he knew it had to be done. He went to Washington on 18 April to tender resignation which was accepted on 23 April to take effect 30 June 1886, and was granted leave until that date. In a letter of 9 October 1886 he mentions going to Philadelphia to see his girl Edith, and bought her an engagement ring sapphire surrounded by diamonds. Also he said they probably wouldn't be married for a year as her mother wanted to take her to Paris for her trousseau, and also thought she was a little young for marriage. However Edith and Louis decided a year was much too long to wait and finally persuaded her family to relent and permit them to be married the following June. Their wedding took place on 28 June 1887, at the Church of the Resurrection, corner of Broad and Tioga Streets in Philadelphia. The ceremony was performed by the groom's father, Rev. Dr. Thomas Duncan, assisted by Rev. Joseph P. Moore. The best man was Dr. William Fox, a cousin of the groom, and the ushers were William Weir McKee and Llewelyn McKee, brothers of the bride, Dr. Gustav Liebig and Ensign Wilkes, U.S.N. The bride wore a dress of heavy white satin, en train, with Valenciennes lace, and carried a bouquet of daisies. She was given in marriage by her father, James Harper McKee.

After a brief honeymoon, they made their home at 1121 Calvert Street in Baltimore, which remained their home for fourteen years. All of her children were born here except Harriet who was born in Philadelphia. Up until the Spanish-American War, Dr. Duncan was Professor of Applied Electricity and Chairman of that Department at Johns Hopkins University. In addition he was continuously engaged in various engineering projects. In August 1898 he returned to his home in Baltimore and resumed his position at Johns Hopkins University and his connections as consulting engineer. As the press of his business in the industrial world was taking more and more of his time, he resigned from the University on 1 May 1899 and became Consulting Electrical Engineer of the Third Avenue Street Railway System in New York, and in charge of the electrification of that system. He was also Consulting Electrical Engineer to the Rapid Transit Commission of New York and supervised the work of electrifying New York City's first subway system. At that time Dr. Duncan was regarded as the most celebrated consulting electrical railway engineer in the world. During the late spring of 1900 his family moved to Pelham Manor, New York, where they occupied a rented home for the summer. In the fall they removed to Plainfield, New Jersey, where they remained until 1902. That year Dr. Duncan was called to inaugurate the Electrical Engineering Courses at the Massachusetts Institute of Technology, and became Head of the Electrical Engineering Department. During his. tenure at M.I.T. his family settled in Brookline, a suburb of Boston. On 20 July 1904 he tendered his resignation "on account or pressure of outside engineering work,” and it was accepted the following day.

He returned to New York where he became head of the Electrical Engineering firm of Duncan and Hutchinson. The family settled in Pelham Manor at 998 Prospect Avenue, in a big, comfortable, three story house with elastic sides, which, will be well remembered by his children and grandchildren. Commuting to New York was easy for him as “998” was only a short walk from the Pelham Manor Station where through trains would stop, upon his request, to pick him up and drop him off on his return home. He held passes for almost all railroads. After his return to New York he also became Chief Consulting Electrical Engineer for the Keystone Company of Philadelphia and the Independent Telephone System in Baltimore and Pittsburgh. Much of that work was in connection with an automatic dialing telephone system for which blueprints were made in 1904. In 1904 he also was the Chairman of the Railway Section, International Electrical Congress at the St. Louis Universal Exposition. He also was Consulting Electrical Engineer for the Cincinnati Traction Company, the Indianapolis and Western Traction Company, The Indiana Union Traction Company and several others in the Midwest. He was forced to do considerable traveling, some trips even taking him to Europe. It was natural that his services were sought in important patent litigations as he was considered an expert in such matters. It is of interest to note that correspondence exists from Stephen D. Field dated 2 and 27 April 1910 concerning inspecting some invention of his in Stockbridge, Massachusetts. Stephen Field was a twin cousin of Admiral Wells L. Field #4 and an inventor of electrical apparatus, holding some 200 patents. Dr. Duncan's partnership with Hutchinson was dissolved and a new consulting engineers firm of "Duncan, Youn and Company" was formed in New York. Dr. Duncan died suddenly on 13 February 1916 at his home in Pelham Manor. lie was buried in the McKee Plot of the Fairview Cemetery at Catasauqua, Pennsylvania, on Wednesday 16 February.

Dr. Duncan was a man of medium build, about 5'11" tall whose carriage was straight and upright. His eyes were blue and his hair had been dark but had turned grey when he was still quite young. He sported a modest, reddish, handlebar mustache, and wore "pince nez" glasses. He possessed a delightful and keen sense of humor. He read a great deal and was clever at drawing cartoons, illustrating the action well. lie was not what one would say was a handy man about the house, as for instance when his wife asked him to fix the door bell, he replied in flippant tones "Woman you better call an electrician, my time is worth $100 an hour." He ran a taut ship and was fairly strict with the children, except for the youngest, to whom he did a fair amount of spoiling.