“Indian Reserve”

A 1775 map of British North America, with the Thirteen Colonies shown in red.

From Wikipedia:

The Royal Proclamation of 1763 was issued by King George III on 7 October 1763. It followed the Treaty of Paris (1763), which formally ended the Seven Years' War and transferred French territory in North America to Great Britain.^[1] The Proclamation at least temporarily forbade all new settlements west of a line drawn along the Appalachian Mountains, which was delineated as an Indian Reserve.^[2] Exclusion from the vast region of Trans-Appalachia created discontent between Britain and colonial land speculators and potential settlers. The proclamation and access to western lands was one of the first significant areas of dispute between Britain and the colonies and would become a contributing factor leading to the American Revolution.