The objectives of this study were to review historically grammar textbooks published through authorization by the government and to show the necessity for research to structure the grammatical knowledge system presented in textbooks, focusing on grammatical education in Korean language education conducted under the rule of the U.S. military government after the Liberation and before the establishment of the Government of the Republic of Korea. In Korean language education after the Liberation, it was difficult to solve at once all problems related to the national curriculum,school system, textbooks, teaching methods, etc. established under the rule of Japanese imperialism, which had promoted the spread of the Japanese language and the shrinkage and removal of the Korean language. Accordingly, research on Korean language textbooks after the Liberation has an important meaning in that it is closely connected to the establishment of the Korean language curriculum and the fundamental framework of Korean language education. Previous studies on Korean language education during this pe riod can be divided into the longitudinal dimension and the horizontal dimension of Korean language education history. Studies in the longitudinal dimension include: ①studies on the formation of the Korean language curriculum and the development of its curricular characteristics(Park Yeong mok, Min Hyeon sik, Kim Jong cheol et al., 2005; Yoon Yeo tak et al., 2006; Oh Hyeon ah, 2011); ② studies on changes in materials included in Korean language textbooks(Jo Hee jeong, 2005a; Jo Hee jeong, 2005b; Jo Hee jeong, 2005c; Seo Myeong hee & Jo Hee jeong, 2006a; Jo Hee jeong & Seo Myeong hee, 2006b;Lee Myeong chan, 2008) and ③studies on changes in the bibliography,unit system and contents of textbooks(Jo Hee jeong, 2011)and on changes in the content areas of the Korean language(Yoo Ok soon, 1995; Ko Yeong geun, 2001; Choi Ho cheol, 2008). Among studies in the horizontal dimension, Choi Hyeon seop(1990) analyzed the materials of novels in textbooks authorized during the period of the U.S. military government, Heo Jae yeong(2005) analyzed secondary Korean language textbooks during the period of the U.S. military government until the announcement of the 1st National Curriculum in 1956, and Jeong Jin heon(2005) studied the types and patterns of traditional fairytales in elementary textbooks focusing on the period of syllabus. Through this study, we found that advanced discussions on the history of Korean language education have not been sufficient and, in particular, discussions on the history of Korean language education in the horizontal dimension have been quite insufficient. Thus, recognizing the problem that studies on Korean language textbooks since the Liberation became crucial foundation for the es tablishment of the identity and framework of the Korean language curriculum under the government led National Curriculum, this study, as preliminary research before full scale studies to restructure the grammatical knowledge system described in grammar textbooks, limited the scope of research to the period of the U.S. military government until the establishment of the Government of the Republic of Korea in the horizontal dimension of Korean language education history and discussed the geopolitical position of such studies in Korean language education and grammatical education and how the grammatical knowledge system can be structured.