Complex sentence: In 1764, King George II set the border between New Hampshire and Vermont as the western bank of the Connecticut River, while concurrently the Royal Board of Trade set exactly the same feature as the border between New Hampshire and New York.
Split into simpler sentences: In 1764, King George II set the border between New Hampshire and Vermont as the western bank of the Connecticut River. Concurrently, Britain's Royal Board of Trade set exactly the same feature as the border between New Hampshire and New York.