In today's digital era, Text Mining technique is widely used in scientific research in general and especially, in History. In historical research and teaching, land ownership is one of the important issues in many agricultural countries like Vietnam. Through the application of Text Mining techniques in data analysis and extraction of information from documentary sources on land ownership at the National Archives Center, the paper will clarify specific values about ownership and land-related historical issues in the Mekong Delta, a region of Vietnam, for 20 years (1955 – 1975). The research results not only provide an important source of reference data for teaching history, but also serve as the basis for research and planning of socioeconomic development strategies in the Mekong Delta nowadays.