The Proclamation of 1763, issued by King George III, was significant for American colonies as it prohibited settlement west of the Appalachian Mountains. This was intended to stabilize relations with Native Americans and avoid further conflicts post-French and Indian War. However, colonists resented the restriction, viewing it as an infringement on their rights to expand and prosper. The Proclamation intensified tensions between British authorities and American settlers, ultimately contributing to the revolutionary sentiment that led to the fight for independence.