1136: Mx. Jan 18, 2018
The abbreviation Ms. was created in the 20th century in order to solve (at least) two problems; first and foremost, it does not require people to either share or be aware of a woman's marital status, which was a double standard given that Mr. never did that anyway, and second it made hypothetical statements or unknown information possible to share without compromising truth or personal comfort. This did take a while to catch on; the title was invented in 1901 and was not adopted by many major publishers until the late 20th century at least. Today Ms. is perfectly common—and possibly encouraged—even if the referent's marital status is well-known.
A modern movement similar to this is with the honorific Mx., much in the same way to how Spanish speakers are now using -X instead of the gendered -O and -A at the end of nouns, which solves the similar problems of not requiring people to be aware of gender, and making hypotheticals (or simply guessing) fairer. Moreover, it also does not assume a binary, which Mr. and Ms./Mrs/Miss all do. With the comparison in mind, it may be a while until major publishers catch on to this trend, but that does not mean, however, that it will not happen. You can now support Word Facts on Patreon for new things and to help make the content better: https://www.patreon.com/wordfacts.