In 1784 Congress recommended to the legislature of the different States the adoption of a resolution prohibiting, for fifteen years, the importation and exportation of every species of merchandise, in vessels belonging to any foreign powers not provided with a commercial treaty with the United States. The people of Boston had been highly exasperated by the exclusion of their vessels from the ports of the West Indies, and by the high duties on rice, oil, and tobacco, while their shipping had also suffered by the British regulations of her fisheries along the American coasts. [Sidenote: Changes produced by the Navigation Laws consequent on the separation.] They overlooked the great fact that the independence of the North American colonies necessarily placed them in the same relative position to Great Britain as other countries affected by the English navigation laws, and thereby excluded them from the ports of the British Colonies, a result deeply prejudicial to the shipping interests of Boston, as their cheap ships could no longer trade with the West India Islands.[237] The high differential duties on rice, oil, and tobacco which had been enforced against them, regulations combined with the fishery, led to retaliatory measures being resorted to by the people of Massachussetts; hence, after the 1st of August, 1785, the exportation of American produce and manufactures was altogether prohibited, and vessels owned by British subjects prohibited from entering the ports of that State. A proviso was indeed added to meet the case when the governor of any British settlement might be willing to rescind the proclamations against American vessels. In fact a new warfare of prohibitions and restrictions, with retaliatory and conciliatory measures to counteract or aid the contending parties as the case might be, was commenced by various States, the end of which was not foreseen upon either side the water. Unfortunately the States of the North of the Union had commercial interests antagonistic to those of the South, and hence arose a complex system which on all sides greatly increased the difficulties of the navigation laws, and became the parent of endless strife and animosity, which in after years assisted in some measure to bring about the terrible civil war that raged from 1860 to 1865 between the Northern and Southern States.