Constitution of the State of Indiana Art. 14, § 1

Section 1. In order that the boundaries of the State may be known and established, it is hereby ordained and declared, that the State of Indiana is bounded, on the East, by the meridian line, which forms the western boundary of the State of Ohio;  on the South, by the Ohio river, from the mouth of the Great Miami river to the mouth of the Wabash river;  on the West, by a line drawn along the middle of the Wabash river, from its mouth to a point where a due north line, drawn from the town of Vincennes, would last touch the north-western shore of said Wabash river;  and, thence, by a due north line, until the same shall intersect an east and west line, drawn through a point ten miles north of the southern extreme of Lake Michigan;  on the North, by said east and west line, until the same shall intersect the first mentioned meridian line, which forms the western boundary of the State of Ohio.