Shipping on the Thames has played a significant part in London's history. By 1700 about 70% or more of England's foreign trade was handled by London, as the mouth of the Thames provided easy access to Europe and other countries. In the 19th century the Thames became very congested. The West India vessels contributed particularly to seasonal congestion as they all arrived between July and October and left by the end of November. The docks were later developed in an attempt to resolve the congestion problem. Plate No.2.