At 3,400 miles, China's second-longest; it is also the most important to the northern half of the country. It rises in Qinghai province and flows into the Bohai Gulf of the Yellow Sea. The river's name comes from the extraordinary amount of loess silt that it carries, an average of 57 pounds for every cubic yard of water. Among its notable features is the Grand Canal, rebuilt during the Ming Dynasty, which links it to the Yangtze.