What area were the English colonies moving into in the Appalachian
Mountains?

The British government did not want American colonists crossing the Appalachian Mountains and creating tension with the French and Native Americans there. The solution seemed simple. They issued the Royal Proclamation of 1763, which declared the boundaries of the thirteen colonies as the Appalachian Mountains.

Crossed by few passes, the Appalachians were a barrier to early westward expansion and played an important role in U.S. history; major east-west routes like the Cumberland Gap and Mohawk Trail followed river valleys or mountain notches.