2. According to China's earliest geographical work Yu Gong, "Zhao Yan" belonged to Jizhou in ancient times.

3. The Spring and Autumn Period was Yan Jin, and the Warring States Period was Yan, Zhao, Zhongshan, Wei and Qi.

4. Qin established Shanggu, Yuyang, Youbeiping, Dai, Julu, Handan, Hengshan and other counties.

5. Since the Han Dynasty, it has been officially named Youzhou and Jizhou.

6. Sui set up the manager of Youzhou.

7. The Tang Dynasty was called Hebei Road, and the Song Dynasty divided Hebei into east and west roads.

8. In the Yuan, Ming and Qing Dynasties, because the capital was located in Beijing, Hebei was an important place in Gyeonggi, Yuan belonged to Zhongshu Province, Ming belonged to North Zhili, and Qing belonged to Zhili.

9. Zhao Yan faces the Great Wall in the north, the Yellow River in the south, Taihang Mountain in the west and Bohai Sea in the east. The topography is diverse, and the natural and human landscapes are rich and colorful.