One 1936 ashram, then yoga centers on five continents
Swami Sivananda Saraswati (1887-1963), a former physician who had practiced medicine in British Malaya, founded the Divine Life Society near Rishikesh in 1936 and went on to author more than 200 books. His disciples later established organizations across North America, South America, Europe, Asia, and Australia, spreading his method through the worldwide Sivananda Yoga Vedanta Centres.
How we know
Sivananda Saraswati: b. 8 Sep 1887, d. 14 July 1963; studied medicine and served as a physician in British Malaya; founded the Divine Life Society 1936 at Sivananda Ashram (Muni Ki Reti, ~3 km from Rishikesh, on the Ganges); author of 200+ books; Sivananda Yoga Vedanta Centres (founded by disciple Vishnudevananda) operate across five continents. (en.wikipedia.org/wiki/Sivananda_Saraswati; dlshq.org)
One of many fact-checked wonders across eight traditions at The Spring of Wisdom.