This study examines the changing trends in fortress-building techniques of early Joseon-period town fortresses (eupseong), with particular attention to the promulgation of the Chukseong Sindo (New Fortress Construction Map) in 1438 (20th year of King Sejong’s reign). Although the Chukseong Sindo itself has not survived, details preserved in a memorial submitted by Lee Bohum reveal that its most distinctive feature was the step-like terracing of the inner wall. Based on both archaeological evidence and documentary records, fortress construction in early Joseon can be divided into three phases: (1) renovation of Goryeo-period earthen ramparts into stone fortresses, (2) adoption of terraced stone inner walls in line with the Chukseong Sindo, later reinforced with earth, and (3) the appearance of vertical inner walls beginning with Gohyeon Eupseong in 1451, alongside continued use of terracing. In summary, early Joseon fortresses typically featured sturdy stone exteriors and terraced or vertical inner walls covered with sloped earth. These standardized methods reflect the Chukseong Sindo’s influence and the centralization of fortress construction as a state-supervised enterprise.