There was a history of Standard ML published as
part of HOPL4 a couple of years ago - https://dl.acm.org/doi/10.1145/3386336
I was particularly interested by the more recent history, after SML '97, where there was plenty of interest in improving the language and its
library, but Milner insisted that there would be no further changes, and the Definition was non-free so the others could not build on it. (It has since become Free though its source code was lost.)
Despite that there is/was an SML Basis Library project, and a Successor ML project, but it looks like even the die hard fans have drifted away
https://smlfamily.github.io/
Despite that there is/was an SML Basis Library project, and a Successor ML project, but it looks like even the die hard fans have drifted away https://smlfamily.github.io/