The Norwegian-Norse chieftain Ingólfr Arnarson built his homestead in present-day Reykjavík in 874. Ingólfr was followed by many other emigrant settlers, largely Scandinavians and their thralls, many of whom were Irish or Scottish. By 930, most arable land on the island had been claimed; the Althing, a legislative and judicial assembly, was initiated to regulate the Icelandic Commonwealth. Lack of arable land also served as an impetus to the settlement of Greenland starting in 986. The period of these early settlements coincided with the Medieval Warm Period, when temperatures were similar to those of the early 20th century. At this time about 25% of Iceland was covered with forest, compared to 1% in the present day. Christianity was adopted by consensus around 999–1000, although Norse paganism persisted among segments of the population for some years afterwards.