啟定帝
In 1836, the prefect concurrently governed 3 districts of Đăng Xương, Minh Linh and Địa Linh. During the Duy Tân Dynasty, the prefecture was just a large district without government. That situation lasted until the dynasties of Minh Mạng, Tự Đức and Khải Định and then was gradually adjusted to become the present land. The geographic adjustment process is as follows: