In 3 to 5 sentences explain the reasons for the proclamation of 1763

The Proclamation of 1763 was issued October 7, 1763, by King George III following Great Britain's addition of French territory in North America after the end of the French and Indian War/Seven Years' War, in which it forbade settlers from settling past a line drawn along the Appalachian Mountains. The purpose of the proclamation was to organize Great Britain's new North American empire and to stabilize relations with Native North Americans through regulation of trade, settlement, and land purchases on the western frontier. The Royal Proclamation continues to be of legal importance to First Nations in Canada and is significant for the variation of indigenous status in the United States. It also ensured that British culture and laws were applied in Quebec, which was done to attract British settlers to Quebec. 
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The last 2 sentences I got from Wiki credit to them

To prevent the colonists from moving west of the Appalachian Mountains.
To prevent another conflict with the indians

The re-election of the president abraham lincoln.