Chomsky's Generative Grammar(Placed at 1955 because I could only find "1950's")
Chomsky's Generative Grammar Theory goes into detail as far as what grammar is. Not only that it is a set of rules put in place to structure a language, but specifically that it is used to make up sentences within that language.
Syntactic StructuresThis book by Noam Chomsky focuses on Generative Grammar. He also expands on the teachings of Zellig Harris' transformational generative grammar model. Reference: Chomsky, N. (2015). Syntactic Structures. Martino Publishing.
Theory of Universal GrammarI put this at 1960 because the only date I could find said "1960's". This theory by Noam Chomsky was stating that regardless of environmental influence, there is always some sort of set of rules that humans place within the language that they speak. Literally meaning, every language has a grammar structure of some kind regardless of the environment of which the language developed.
Theory of LanguageNoam Chomsky states in his theory of language that humans are born with the natural ability of comprehending and learning language. Also, that these all languages have a similar structure and set of rules. Language is too complex with different variations between sounds, tones, pronunciation, etc. that it is impossible to simply learn through environmental experience alone.
Chomsky's Acquisition of Language
Noam Chomsky's "The Minimalist Program"Noam Chomsky is found to go along side the rationalist point of view when it comes to philosophy. This means that he disagrees with the empiricist point of view that everything is discovered or known through experience. He believes that language is not fully dependent on observation alone. He talks more about this in his book "The Minimalist Program".
Chomsky, Noam (1995). _The Minimalist Program_. MIT Press.