There's no set rule for picking a state capitol.\n\nMost capitols were set long ago, in a place central to a state.  This is because state representatives and officials had to ride, by horse and/or carriage, to the capital to conduct business.  I live in Michigan.  Lansing is out capital.\n\nWhile Detroit is our biggest and most popular city, it wouldn't be practicle for a representative to ride from, say, Marquette.  \n(This is actually a poor example because Detroit was the capital of Michigan before Lansing, but the point is the same.)