Why in many US states the biggest city is not the capital?

[muon2]

Springfield IL became the capital through a political power play. Kaskaskia was the first state capital, but it was soon moved to Vandalia. There was grumbling over the condition of the Vandalia capitol, and the city pushed through spending for improvements. State Representative Abe Lincoln and allies from the Sangamon county area got a provision added to a funding bill that provided for a new capitol in Springfield. Political shenanigans are nothing new in IL.

[muon2]

Springfield Illinois also has a ridiculous shape:



It is the red area.

No more so than the capital of OH. Many states have annexation laws that let cities grow where developers want to build and leave holes where there is less economic value or older small incorporated areas that are not interested in consolidating. Springfield stands out in that election map because by law the city is in its own township (Capital township) and the township grows with the city.