Proposed state of Lincoln
Idaho makes no sense. I speak from experience, having lived in the state for 20 years. Because it was cobbled together from leftovers, Idaho’s regions have nothing in common—they go together about as well as peanut butter and jellyfish.
This problem was understood as far back as 1886, when a bill was passed by Congress that would have eliminated Idaho altogether—giving the south to Nevada and the north to Washington. Alas, President Grover Cleveland vetoed the measure.
In 1907, the best plan of all was proposed, creating the state of Lincoln from northern Idaho and eastern Washington. This brilliant plan not only solved the Idaho problem, but it also made more sense of Washington and Oregon—because both of those states are profoundly divided by the Cascade mountains.