William, Earl of Douglas, acquired the barony of North Berwick in 1371 and laid the foundation of the long, extensive and powerful influence of the Douglas family in East Lothian. It was forfeited in 1455 by James, Earl of Douglas; but in 1479 it was granted by James lll, with most of the forfeited estates of that earl, to his heir Archibald, Earl of Angus and erected into a free barony. It was sold by the Marquis of Douglas to Sir Hew Dalrymple, Lord President of the Court of Session in 1694 and remains in the ownership of his descendants. The original charter of Royal Burgh was granted to the town in 1373 during the reign of Robert III, but this was suppressed by William, Earl of Douglas who held the barony of North Berwick during that period. The Earl refused to implement the charter because he might lose his right of superiority over the port and burgh. Although at this time the main trade was wool and only small amounts were being exported. Even at its peak in 1429 only ten tons of wool were exported yearly.

The charter now in existence was granted by James VI on 18th September 1568. In that charter mention is made of the original document being destroyed by fire. It narrates 'calling to mind that our predecessors of good memory did of old erect and make our burgh of North Berwick into a free royal burgh, and that the ancient infeftment thereupon granted to them by our said predecessors in the time of the burning of the said burgh by the English was burnt and destroyed, and so cannot readily be found. We with consent of our Regent foresaid (James, Earl of Murray) have erected, made, and confirmed, as by the tenor of our present charter we erect, make, and confirm, the said town of North Berwick into a free royal burgh.' A ratification of this was passed again in 1609.

King Robert III during his reign honoured the town with his presence. In 1404, Prince James with his protector Sir David Fleming passed through North Berwick on his way to the Bass Rock, where he was to embark for France for his education and safety. In 1491, Bothwell accompanied by the Bishop of Glasgow also found North Berwick a convenient port of embarkation when on a mission to the continent to find a queen for James IV.