Final answer:
The mountain range that served as the base for the Proclamation of 1763 line is the Appalachian Mountains.
Step-by-step explanation:
The mountain range that is the Eastern Continental Divide and was used as a base for the line in the Proclamation of 1763 is the Appalachian Mountains. The Proclamation of 1763 was issued by the British government to prevent further conflicts with Native American tribes. The proclamation drew a line along the crest of the Appalachian Mountains, prohibiting British colonists from settling west of the mountains.
Learn more about Appalachian Mountains and the Proclamation of 1763