You didn’t know, because it started with Gloria Steinem in the 70s.
Wikipedia tries to make it sound like it’s some old tradition, but it’s actually fairly new, with the prior historical references being obscure until it was resurrected. It’s right there in the article:
> “Ms. was another acceptable, but rarely used, abbreviation for Mistress in England in the 17th and 18th centuries.[12] During the 19th century, however, Mrs. and Miss came to be associated almost exclusively with marital status,[13] and Ms. was popularized as an alternative in the late 20th century“
It was actually Sheila Michaels in the 1960s who initially started the push for it: https://en.wikipedia.org/wiki/Sheila_Michaels
Gloria Steinem cofounded Ms. Magazine in the early 70s which helped popularize it further.
Anyway, how old are you that well over half a century is “fairly new” to you? Do you still wear galoshes and use a mimeograph?
Fairly new? Using "Ms" has been standard practice in the New York Times for 40 years, and it was regarded as a holdout at the time.
https://www.nytimes.com/2017/04/06/insider/1986-ms-joins-the...