The Yongle Emperor ( 1402¨C1424) restored the Grand Canal in the Ming era.
The Grand Canal was renovated almost in its entirety between 1411 and 1415 during the Ming Dynasty (1368¨C1644). A magistrate of Jining, Shandong sent a memorial to the throne of the Yongle Emperor protesting the current inefficient means of transporting 4,000,000 shi (428,000,000 liters) of grain a year by means of transferring it along several different rivers and canals in barge types that went from deep to shallow after the Huai River, and then transferred back onto deep barges once the shipment of grain met with the Yellow River. Chinese engineers built a dam to divert the Wen River to the southwest in order to feed 60% of its water north into the Grand Canal and the other percent heading south. They dug four large reservoirs in Shandong to regulate water levels, which allowed them to avoid pumping water from local sources and tables. Between 1411 and 1415, a total of 165,000 laborers dredged the canal bed in Shandong, built new channels, embankments, and canal locks.
The Yongle Emperor moved the Ming capital from Nanjing to Beijing in 1403. This move deprived Nanjing of its status as chief political center of China. The reopening of the Grand Canal also benefited Suzhou over Nanjing, since the former was in a better position along the main artery of the Grand Canal, hence it became Ming China's greatest economic center.The only other viable contender with Suzhou in the Jiangnan region was Hangzhou, but it was located 200 km (124 miles) further down the Grand Canal and away from the main delta. Even the shipwrecked Korean Choe Bu (1454¨C1504)¡ªwhile traveling for five months throughout China in 1488¡ªacknowledged that Hangzhou served not as a competitor but as an economic feeder into the greater Suzhou market. Therefore, the Grand Canal served to make or break the economic fortunes of certain cities along its route, and served as the economic lifeline of indigenous trade within China.
The scholar Gu Yanwu of the early Qing Dynasty (1644¨C1912) estimated that the previous Ming Dynasty had to employ 47,004 full-time laborers recruited by the lijia corv¨¦e system in order to maintain the entire canal system. It is known that 121,500 soldiers and officers were needed simply to operate the 11,775 government grain barges in the mid 15th century.Besides its function as a grain shipment route and major vein of river borne indigenous trade in China, the Grand Canal had long been a government-operated courier route as well. In the Ming Dynasty, official courier stations were placed at intervals of 35 to 45 km.Each courier station was assigned a different name, all of which were popularized in travel songs of the period.