Garter Snakes can be found in a whole lot of places and they've been seen in most of the United States.
Although garter snakes can be found in most if not all parts of the USA in all states the garter snake is mostly found in and prefers to live in woodlands, meadows and grassy knolls and they also like to be near water, especially "in the arid parts of the West.
I've encountered a garter snake in Kansas before when I was on a trip there and I also encountered a garter snake in Oklahoma and Arkansas on my way through there at rest stops before.
Garter snakes although can be scary the garter snake are not harmful to humans other than biting them and causing a painful bite.
But the venom that a garter snake puts in your body is not deadly or poisonous to humans.
I've never been bitten by a garter snake before but my mom has and she said the garter snake bit her once and then tried to bite again as they tend to chew on you rather than just snap at you.
She got bit by the garter snake while gardening and she was just fine other than having the bite.