Mr. Mason alludes in this passage to the vicissitudes suffered by the small military post or "tomahawk fortress," as such posts on the frontier were sometimes called, at the mouth of the St. Joseph River, which during the troublous period of the eighteenth century had frequently changed masters. At the time of which we are writing, the fort, or the remains of a fort, at that point was in such a condition that a new structure would have been necessary if that site had been determined upon by the authorities. Building operations for Fort Dearborn began on the Fourth of July, under the direction of Captain Whistler. The soldiers cut the timber required from the neighboring forests and, as there were no horses or oxen available in the vicinity, the men dragged the logs with ropes from the woods to the banks of the river, and floated them to the site chosen. At that period a forest of considerable density covered the land on the north side of the river, and there was also a fringe of trees along the South Branch throughout its entire length; but the extensive area in the South Division, excepting the woodland on the margin of the river, was open prairie. In fact, the Grand Prairie of Illinois, extending for hundreds of miles into the interior of the state, here reached the shore of the lake for a space of three or four miles along the water, and it is a singular fact that at no other place does the Grand Prairie border on Lake Michigan. It was on the line of this famous tract that the massacre occurred, which will be described in the following pages. The portion of the Grand Prairie between the mouth of the river and a point some three or four miles south along the lake shore was mostly devoid of trees, a scanty growth of cottonwoods and pines, however, maintaining a precarious existence among the sand-dunes. A mile or two south of the river's mouth these low sand-hills became the predominant feature of the landscape, just as may be found at the present time along the low shores of the lake beyond the city limits toward the south and east. Behind the sand-hills the level prairie stretched away as far as the eye could reach. Schoolcraft, in one of his early voyages, related that as one approached the shores from the southern end of Lake Michigan, the appearance of these sand-dunes--between which was occasionally seen a scanty growth of stunted pines--gave a desolate aspect to the scene, in wonderful contrast with the rich and abundant verdure of the far-reaching prairie land lying just beyond them.