Amsterdam has a long and eventful history. The origins of the city lie in the 13th century, when fisherman living along the banks of the River Amstel built a bridge across the waterway near the IJ, then a large saltwater inlet. Wooden doors on the bridge served as a dam; these protected the town from the IJ, which often flooded the early settlement. The mouth of the river Amstel, where the Damrak now is, formed a natural harbor, which became important for trade.
The oldest document that refers to the settlement of Aemstelledamme 'dam on the Amstel', as it was then known, is dated 1204 AD.