The most common way of dividing the regions of the Black Forest is, however, from north to south. Until the 1930s, the Black Forest was divided into the Northern and Southern Black Forest, the boundary being the line of the Kinzig valley. Later the Black Forest was divided into the heavily forested Northern Black Forest, the lower, central section, predominantly used for agriculture in the valleys, was the Central Black Forest and the much higher Southern Black Forest with its distinctive highland economy and ice age glacial relief. The term High Black Forest referred to the highest areas of the South and southern Central Black Forest.