Thayer Lindsley was born on August 17, 1882 in Yokohama, Japan to John Lindsley (1845-1909), a representative for the Canadian Pacific Railway in Japan, and Virginia Thayer Payne (1856-1841). The Lindsley family eventually returned to the United States of America (U.S.A.) and moved to Milton, Massachusetts, a suburb of Boston, Massachusetts. Thayer Lindsley attended Milton Academy, a private college preparatory school in Milton. In 1903, he graduated with a Bachelor of Arts (B.A.) from Harvard University in Cambridge, Massachusetts and in 1904 he graduated from Harvard with a degree in Civil Engineering (C.E.).
After graduating from Harvard, Lindsley worked as a civil engineer for the New York Rapid Transit Commission, where he was involved in the construction of the Brooklyn-Manhattan subway; however, his older brother, Halstead Lindsley, was a mining engineer and Lindsley became fascinated with the subject. He took a few geology courses at Columbia University, but most of his knowledge was learned working in mining and as a prospector in the western United States between 1906 and 1914. In 1914, Lindsley discovered the Iron Dyke Mine in Oregon and ran it for Goodzich, Lockhard and Company for three years, until he joined the American Expeditionary Force as an artillery officer when the U.S.A. joined World War I (WWI).
After WWI, Lindsley returned to the Iron Dyke Mine and remained there until 1924. He had received a stake of $30,000 in the Iron Dyke Mine, which he decided to invest in mining in Canada. With a partner, Joseph Errington, Lindsley began exploring areas of Northern Ontario for viable mining prospects. In 1926, the pair staked claims around the Vermilion River, near Sudbury, Ontario, and founded Sudbury Basin Mines.
In 1928, Lindsley founded Falconbridge Nickel Mines Limited in Falconbridge, Ontario after purchasing the land claims from Bennett-Longyear for $2,500,000, the most ever paid at that time for a mine in the Sudbury area. Falconbridge Nickel Mines Limited was a subsidiary of Ventures Limited, Lindsley’s holding company that he established in 1928 with his brother, Halstead Lindsley, and associates, Joseph Errington, Col. C.D.H. MacAlpine and Gen. D.M. Hogarth. Falconbridge was Venture’s biggest holding and it became one of the world’s biggest nickel mining operations.
In 1929, Thayer Lindsley married Ida Ann Machin, the daughter of a mining executive, in Kenora, Ontario. The marriage lasted until 1935, when Ida Ann Machin went to Reno, Nevada to file for a divorce. The divorce was made legal in Canada by a court in Port Arthur, Ontario in 1936.
Lindsley is known as one of the 20th Century’s most prolific mining developers and executives and was given the nickname “Mr. Mining.” Near the height of his career, in the 1940s-1950s, he was president of ten companies (including the large holding company, Frobisher Inc.), served as a director for fifteen others and held interests in upwards of fifty more companies. Lindsley found or was involved in the development of the following mines: Sherritt Gordon Mine, Manitoba; Giant Yellowknife, Northwest Territories; Beattie Gold Mine, Quebec; Whim Creek, Australia; Connemara, Southern Rhodesia; United Keno, Yukon; Canadian Malartic, Quebec; La Luz, Nicaragua; New Calumet, Ontario and Coniaurum near Porcupine, Ontario.
Lindsley retired as president of Ventures Limited in 1955 and as president of Falconbridge Nickel Mines Limited in 1956. He remained a director on the board of Falconbridge Nickel Mines Limited until 1967, when he was given the title of Director Emeritus.
Thayer Lindsley died on May 29, 1976 at his home in New York, New York. He is buried with his parents, John Lindsley and Virginia Thayer Lindsley, in Milton Cemetery in Milton.