Thompson River, 489 km long, rises in the Cariboo district of the Rocky Mountains and flows south as the North Thompson River. It is joined at Kamloops by the South Thompson R from Shuswap Lk, and the 2 flow united, carrying their blue-green waters into the Fraser River at Lytton. The banks of the lower course are hilly and almost barren, except for sagebrush, and many of the spectacular terraces are used for cattle grazing and fodder crops. Both the CPR and CNR transcontinental lines follow the river from Kamloops to Lytton. Simon Fraser mistakenly believed that David Thompson had found the river, and named it for him.