What natural feature help from the boundary between british and spanish territory in 1763?

The natural feature that helped form the boundary between British and Spanish territory in 1763 was the Mississippi River.

The Treaty of Paris, signed in 1763, officially ended the Seven Years' War. In this treaty, France ceded all of its territory east of the Mississippi River to Great Britain, including Canada and most of the Ohio Valley. Spain, which had allied with France, received the territory west of the Mississippi River, including Louisiana.

The Mississippi River thus became a defining natural boundary, dividing the vast territories of the two European powers in North America.