One of the best ways to become aware of alternate spellings of places is to know how a local would say the place name. There is a San Jose in Illinois and California and they are not pronounced in the same way. Any location named after a member of the Taliaferro family is more likely to rhyme with “fur” that with “arrow.”
And we won’t even get started with how Keokuk, Iowa, is pronounced by locals and non-locals alike.
But if you don’t know how they probably said it, you don’t know all the potential ways it could have been spelled.