Harmless, if you mean non-poisonous, yes.

But they will bite if threatened! I followed a garter snake until it crawled under a trailer...when I stooped down to look, he poised like a cobra and was ready to strike.

Their attack stance may look scary and dangerous...and they WILL bite...but don't panic if you're bitten. You may bleed from the punctures of their tiny teeth but you'll be fine.

The most recognizable feature is a stripe along the spine, for the entire length of the snake; the body itself can be different colors, mainly green or brown.

So once again: garter snakes are not venomous or dangerous; they will defend themselves if threatened and strike. If you're not sure it's a garter, just leave the snake alone.