Some time ago in my ongoing reading of the 1964 Funk & Wagnalls Standard Reference Encyclopedia, in the entry on Arizona, I found this conundrum. The entry states that Arizona is "bounded on the N. by Utah, on the E. by New Mexico, on the S. by Mexico, and on the W. by California and Nevada." But what about Colorado? I asked myself, looking at the map. There it is at the N.E. corner. The boundary lines cross do they not?
This is probably a mathematical question. If the boundary lines have no thickness and the point where they intersect is 0 in dimension, I guess you could argue there is no point at which the two states touch. But such a point does not exist in reality. It must be possible for people to cross from one state to the other at this point. Were Funk & Wagnalls just wrong to exclude Colorado as one of the states that bounds Arizona? Or is this a principle in geography--states or any locations that are kitty corner to each other are not considered to share a boundary? What do people in Arizona and Colorado think about this?