John Todd McMahon was born in Columbia, Maine on 5 May 1843; when very young his family moved west to Lima, Livingston Co., New York, where John was raised. His father, Isaiah McMahon, was an immigrant from Ireland and a Methodist Episcopal clergyman. In September 1862 McMahon was mustered in to Co. E, 136th New York Infantry, with whom he served until June 1865, rising to 1st sergeant. After the war McMahon attended Genesee College at Lima, and in 1870 was ordained into the Methodist Episcopal ministry. On 22 August 1870 McMahon married Sarah Eliza Douglas, with whom he entered the Church's India Mission, established in the 1850s in the British North Western Provinces and Oudh. In November 1870 the McMahons arrived in India and travelled to the missionary station at Roy Bareilly in Oudh (now Raebareli, Uttar Pradesh state), where there was a girls' orphanage, a hospital, and a theological school. McMahon would remain with the India Mission (renamed the North India Mission in 1877) for most of the next 26 years, first at Roy Bareilly (1871-1880) and later at Pauri in the Mission's Kumaon District (now in Uttarakhand state). By 1889 he was responsible for the stations in tha Pauri Circuit and travelled regularly to other stations in the district (Naini Tal, Dwarahat, Kainoor, Pithoragarh). McMahon died in Dwarahat on 5 July 1896. Sarah McMahon remained in India until January 1897 when she and her five sons returned to America and settled in Middlesex, Connecticut. She died on 22 February 1915, in Little Falls, New Jersey.