The calls check — the one joint the text leaves open

Treaty of Chicago (1821), Art. 1; Treaty with the Potawatomi (1826), Art. 1, second cession

Read from the texts aloneThe southern limb is closed by the text: the due-east line from Lake Michigan's southern extreme is a latitude the ground clears by miles. The western limb is the joint: the 1821 polygon's western side in this longitude band is its first call, a segment "running thence south" from "a point on the south bank of the river St. Joseph of Lake Michigan, near the Parc aux Vaches, due north from Rum's Village" — and the treaty gives that point no longitude, bearing or monument. The ground is inside the 1821 cession if it lies east of that segment; every locating carrier reached places the Parc aux Vaches in the Bertrand/Niles reach, west of the town, and the plotted mapping — whose boundary at this latitude stands at ≈86.288° W — puts the segment there. The same joint stated from the other side is the 1826 second cession (7 Stat. 295): a ten-mile strip from the lake eastward "to the land ceded by the Indians to the United States by the treaty of Chicago," south with that boundary ten miles, and back — the strip fills the ten-mile band west of the 1821 polygon and stops at its boundary, short of Roseland by the same 1.9 miles. The 1821-versus-1826 attribution for this townsite therefore turned entirely on that one unlocated-in-text meridian, and it is the plot, not the calls alone, that closes it. The settler of record for the calls side stands named: the Royce Area 117 plat and the federal survey notes for the treaty boundary.