Great Britain and the United States had ignored Spain when they declared in the treaty of peace that the Mississippi, from its source to the Gulf, should remain for ever free and open to citizens of both countries. Perhaps because she was disappointed in not getting a portion of the middle valley away from the Americans in the course of the peace negotiations, Spain soon began to show that she was at least mistress of the lower part of the river. Just where her dominion began was uncertain. During the war, a Virginia captain raised his colours on the Mississippi a few miles above Natchez. A Spanish commandant buried a box near the same spot with the colours of his sovereign as a token of possession. After 1783, the flatboatmen, who adventured down the river with loads of tobacco, flour, or planks, seeking a market at New Orleans or adjacent settlements, found at the Walnut Bluffs, about ten miles below the mouth of the Yazoo River, a post of Spanish customs guards. These bade them lower their flag and put themselves under the protection of the governor of Natchez before proceeding. If the goods escaped paying a duty at this place, they were examined a second time when they reached the group of about one hundred houses, crowning the bluff, which constituted the city of Natchez. On a prominent point, commanding a view of the river for many miles, stood the governor's palace and the fort, at which were usually stationed about a score of Spanish troops. The hardy frontiersmen, who escaped the perils of navigating the river as far as Natchez, bore the inspection and frequent seizure of their goods as a great hardship and unwarrantable action. Scarcely had trade opened after the war before Congress received a complaint from one Fowler that his flatboat loaded with produce for the New Orleans market had been seized for refusal to pay duties at Natchez. A few months later, Thomas Amis, a North Carolina trader, reported the seizure of his stock at the same point, consisting of 142 Dutch ovens, 53 pots and kettles, 34 skillets, 33 cast boxes, 3 pairs dog irons, a pair of flat irons, a spice mortar, a plough mould, and 50 barrels of flour.