At the Falls of the Ohio, Clark established his second base of operations on a long, narrow island afterward known as "Corn Island," that then lay above the falls where the Pennsylvania Railroad Bridge now spans the river. (The name, which was adopted after Clark's occupancy, seems to have been borrowed from a tradition that the first corn in that region was raised there. The island is described as a narrow tract about four-fifths of a mile long by five hundred yards at its greatest breadth. If it now existed the Pennsylvania Railroad Bridge from Jeffersonville to Louisville would pass directly over it. A heavy timber growth originally protected it from the ravages of the river, but with the removal of this protection, it gradually disappeared until washed away entirely. Colonel R. T. Durrett, of Louisville, did what he could to get that city to protect the historic spot. But without avail.) The falls, as being the dividing place between the upper and lower river, was deemed the logical point for a permanent defensive post. Clark's reason for settling on the island, at least temporarily, was two-fold - better protection from hostile bands of Indians and the more effective guarding against desertion, which danger would probably follow the announcement of the commander's real plans. The sagacity of the latter surmise was not at fault in this, as the sequel showed.

The settlement on Corn Island consisted of a sufficient number of rude cabins built from the timber growing on the island, and it took on the character of a real "settlement" by virtue of the families that had thus far accompanied the expedition, which were now apportioned ground for gardens, and an interesting passage in "Clark's Memoir" is to the effect that when word was carried back to the people on the Monongahela "great numbers moved down," and that this was "one of the principal causes of the rapid progress of the settlement of Kentucky."

Clark lingered at Corn Island the better part of June 1778, still hoping to swell his little force, but with disheartening results. According to William H. English, who is the leading authority on all relating to this campaign, relates in his "Conquest of the Northwest" that "it is probably a fair conclusion that Clark brought with him to the falls about one hundred and fifty men; that thirty-five or forty were added to his forces while at the falls; that he left not exceeding ten guards on Corn Island and took with him on the Kakaskia campaign about one hundred and seventy-five men. It is possible that the officers should be added to the number, but it is the author's belief that the effective force with him in the campaign against Kakaskia did not at any time exceed two hundred, which was certainly less than half the number he at one time expected."