Character brick at Simatai Great Wall

The character bricks on Simatai Great Wall are engraved with "Made in Ningxia in the Fifth Year of Wanli", which means that this batch of city bricks was cast in the fifth year of Wanli, and Wanli is the reign title of Zhu Yijun, Emperor Mingshen (September 4, 1563-August 18, 1620), which was used in Ming Dynasty for 48 years (1572-1620), the longest used reign title in Ming Dynasty. These are city bricks cast in Ningxia during this period.