What are some of the good textbooks on Modern Monetary Theory and the Development of Monetary Theory? I am trying to study modern monetary theory for my research. Recommendations, please? Thank you!
You ask for sources on MMT and then sources on development of monetary theory. I don't know about the former (but I know there are some users here who are fans of MMT so hopefully they will hook you up with some good sources) but when it comes to the latter then a classic text that covers development of contemporary monetary theory is Walsh Monetary Theory and Policy (The MIT Press).
It is probably one of the most comprehensive textbooks that cover monetary theory all the way  to the most recent advances. It unfortunately does not cover MMT because it is not an accepted theory in profession but has very good treatment of development of monetary theory all the way from canonical models to present day state of the art models.