ANIMAL NEGLECT...Laws, ordinances, rules, regulations?

In brief, I would like to know where to begin finding answers
to my questions about pet owners who could give a hoot if
their dog lays in the freezing cold without so much as a cardboard
box for shelter.

I've called the police, they refer me to the sheriff, who
refers me to animal agencies, of which there seem to be
none. Even the local vet doesn't seem to know where to begin.

Sadly, this one dog is but the start of a long list of animals left
in the cold, chained to a tree, no dog house, no blanket, NOTHING.

So I ask you. Where do I begin. Does each city decide how much
animal neglect is 'tolerable'.