Washington, in the autumn of 1784, after his retirement to Mount Vernon, made a tour into the Western country, for the express purpose of ascertaining by what means it could be most effectually bound to the Union. The policy of opening communications eastward, by means of the rivers flowing through Virginia to the Atlantic Ocean struck him at once. On his return, he addressed a letter to the Governor of the State, in which he recommended the appointment of a commission, to make a survey of the whole means of natural water communication between Lake Erie and the tide-waters of Virginia. He does not seem at this time to have considered the navigation of the Mississippi as of great importance; but he thought rather that the opening of that river would have a tendency to separate the Western from the Eastern States.[323] A year later, he held a clear opinion, that its navigation ought not at present to be made an object by the United States, but that their true policy was to open all the possible avenues between the Atlantic States and the Western territory, and that, until this had been done, the obstructions to the use of the Mississippi had better not be removed.[324] Those obstructions, however, involved the hazard of a loss of the territory to which the navigation of that river had already become extremely important. Their nature is, therefore, now to be explained. The Treaty of Peace with Great Britain recognized, as the southern boundary of the United States, a line drawn from a point where the thirty-first degree of north latitude intersected the river Mississippi, along that parallel due east to the middle of the river Appalachicola; thence along the middle of that river to its junction with the Flint River; thence in a straight line to the head of St. Mary's River; and thence down the middle of that river to the Atlantic Ocean.[325] At the time of the negotiation of this treaty West Florida was in the possession of Spain; and a secret article was executed by the British and American plenipotentiaries, which stipulated that in case Great Britain, at the conclusion of a peace with Spain, should recover or be put in possession of West Florida, the north boundary between that province and the United States should be a line drawn from the mouth of the river Yassous, where it unites with the river Mississippi, due east to the river Appalachicola.[326] The treaty also stipulated, that the navigation of the Mississippi, from its source to the ocean, should for ever remain free and open to the subjects of Great Britain and the citizens of the United States.[327]