Of Toronto, was born at Warwickmains, Ayrshire, Scotland, on the 6th November, 1835. He is the second son of the late Alexander Ralston Langmuir, who married Miss Jane Woodburn, of Aird. Both his maternal and paternal ancestors were well known old Ayrshire county families. Mr. Langmuir was educated at Osbirne's Academy, Kilmarnock, and came to Canada in 1849, when only fifteen years of age. In accordance with the old Scotch system, he was placed for five years with the firm of Miller & Brothers, who then carried on a large mercantile business at Picton, in the County of Prince Edward, as well as in the City of Kingston. Having served his time in both these places, he acquired in 1853, the Picton business, which formerly was carried on by the firm, which along with the building of vessels for the lake trade, together with a large produce business, he carried on from 1853 to 1867. During that time he passed through all grades of municipal office, having served the town of Picton as councillor, reeve and mayor. In 1868, Mr. Langmuir, was appointed, by the Sandfield-Macdonald administration, to the position of Inspector of Prisons and Public Charities for Ontario. Prior to Confederation, there were four inspectors for the Provinces of Ontario and Quebec, and when the Act creating the office for Ontario was under the consideration of the legislature, fears were expressed that one inspector could not perform the work. These fears, however, were groundless, for Mr. Langmuir discharged the onerous and responsible duties of his position, not only to the entire satisfaction of the three administrations under which he served, but to the public generally. A review of his fourteen years of official labour would practically comprise a history of Ontario's public institutions' system. His reports to the legislation number fourteen large volumes, aggregating 4,000 pages of printed matter. No less than eight important public institutions were founded and organized under his supervision and direction during his term of office, viz: The Asylums for the Insane at London and Hamilton; the Asylum for Idiots at Orillia; the Institution for the Deaf and Dumb at Belleville; the Central Prison; and the Mercer Reformatory and Refuge at Toronto. In 1882, Mr. Langmuir resigned his government office, and associated himself with a number of prominent and wealthy men, in the establishment of the Toronto General Trust Company. The position of general manager of this company he now holds. He is also a director of the Federal Bank of Canada, and is one of the Niagara Falls Park commissioners. He is likewise president of the Homewood Retreat Association, a private asylum lately established in Guelph, Ont. Mr. Langmuir has always exhibited a wide public spirit, and devoted much of his attention to municipal politics while a resident of the Bat of Quinté region. At the age of twenty-four, he was mayor of Picton, and with sanguine brilliancy, those who remember him then do say, he added practical wisdom and solid parts. In military matters, he has always taken a deep interest. He was major of the 16th Battalion, and served during the Fenian raids of 1866. In politics, he is a Liberal, believing that the principals adopted by the reform party must in the end prevail and prove the best for the country's welfare. He has travelled over the greater part of the American continent. In religion, he is a Presbyterian, as have been his ancestors for many generations. He has been married three times; first to a daughter of the late Dr. Fairfield, of Prince Edward; second, to a daughter of Mr. John Ridout, registrar of the County of York; and third, to Mrs. Ludlow, a daughter of the late Mr. John Bloodgood, of New York. He has five sons and four daughters. Mr. Langmuir is genial and kind hearted in the domestic and social circles, and lacks not love, honour and troops of friends.

David O'Reilly noted: