Federal highway numbering system -- I-435 and I-635?

Question

I-635 designates a highway that circles (more or less) around the core of Metropolitan Greater Kansas City. A larger circle (more or less) that extends around an ever larger area is numbered I-435. Seems to me the numbering is backwards. Seems to me I-435 ought to be closer in, and I-635 further out, to allow for future growth for an I-835.

Answer 1

What likely happened was that I-635 did not exist in the original plan for interstate expansion in the Kansas City area, but I-435 did.  They found later that a closer-in loop was desired, and because they could not use I-235 (Wichita), the next logical choice was I-635.