This is an orb weaver spider, notice the nice orb web it is on. There are a number of species we have in Kentucky with the black and yellow garden spider reaching two inches with its body, much more with its legs.
So with what you have read with this spider on your porch, did they measure just the body or are they including the legs? This looks to be a barn spider, and I have seen these with a body alone of more than an inch. With the legs it is considerably larger.
Ric Bessin (UK Entomology)