Giant Leopard Moth caterpillar

I agree I believe it's a Giant Leopard Moth, Ecpantheria scribonia

Turtlesandtombstones seems to be on the right track, but that's just my opinion. I think it might be Hypercompe scribonia: https://www.google.com/search?q=hypercompe+scribonia&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=wpydUYTfAvWq4AP5vIGYBg&biw=851&bih=449&sei=xpydUY2cCs754APs64DQAw#imgrc=_

None of the pages I have read about Wooly Bear caterpillars ever say it can be all black, but several of them do mention that the coloring cages as it ages. The following is quoted from http://digitalheritage.org/2011/04/woolly-worms/ "Since their coloring is based on how long the caterpillar has been feeding, plentiful food results in a narrower middle section and longer (wider), dark-colored tips. Woolly worms shed their skins or “molt” six times before reaching adulthood. After each molt their coloring becomes less black and more reddish, so coloring also indicates age. Furthermore, there are over 250 species of tiger moths, so many of the apparent color variations found in woolly worms are often the result of happening upon a different species. However, the true woolly worm of the Isabella Tiger Moth has the stripes mentioned above, alternating between black and lighter shades."

Maybe a leopard moth caterpillar.