When Monterey Leroy Leach was born on 27 May 1849, in Leon, Cattaraugus, New York, United States, his father, Allen Leach, was 22 and his mother, Mary Brand, was 25. He married Harriet A. Calkins on 5 July 1873, in Hortonville, Outagamie, Wisconsin, United States. They were the parents of at least 6 sons and 6 daughters. He lived in Qu'Appelle, South Qu'Appelle No. 157, Saskatchewan, Canada in 1906 and Kootenay County, British Columbia, Canada in 1911. He died on 12 March 1913, in Grand Forks, Kootenay Boundary, British Columbia, Canada, at the age of 63, and was buried in Grand Forks, Kootenay Boundary, British Columbia, Canada.