The tradition of raising stones that had runic inscriptions first appeared in the 4th and 5th century, in Norway and Sweden, and these early runestones were usually placed next to graves. The earliest Danish runestones appeared in the 8th and 9th centuries, and there are about 50 runestones from the Migration Period in Scandinavia. Most runestones were erected during the period 950-1100 CE, and then they were mostly raised in Sweden, and to a lesser degree in Denmark and Norway.
For men of consequence a mound should be raised to their memory, and for all other warriors who had been distinguished for manhood a standing stone, a custom that remained long after Odin's time.
What may have increased the spread of runestones was an event in Denmark in the 960s. King Harald Bluetooth had just been baptised and in order to mark the arrival of a new order and a new age, he commanded the construction of a runestone. The inscription reads
The runestone has three sides of which two are decorated with images. On one side, there is an animal that is the prototype of the runic animals that would be commonly engraved on runestones, and on another side there is Denmark's oldest depiction of Jesus. Shortly after this stone had been made, something happened in Scandinavia's runic tradition[according to whom?]. Scores of chieftains and powerful Norse clans consciously tried to imitate King Harald, and from Denmark a runestone wave spread northwards through Sweden[according to whom?]. In most districts, the fad died out after a generation, but, in the central Swedish provinces of Uppland and Södermanland, the fashion lasted into the 12th century.
There are about 3,000 runestones among the about 6,000 runic inscriptions in Scandinavia. There are also runestones in other parts of the world as the tradition of raising runestones followed the Norsemen wherever they went, from the Isle of Man (Manx Runestones) in the west to the Black Sea in the east (Berezan' Runestone), and from Jämtland in the north to Schleswig in the south.
The runestones are unevenly distributed in Scandinavia: Denmark has 250 runestones, Norway has 50 while Iceland has none. Sweden has as many as between 1,700 and 2,500 depending on definition. The Swedish district of Uppland has the highest concentration with as many as 1,196 inscriptions in stone, whereas Södermanland is second with 391.