Tammy, it's not ringing a bell with me, but I will urge you to post in the Butterfly Gardening Forum, where you will find several knowledgable butterfly and moth experts. They protect their caterpillars over there so don't refer to them as pests.

Many hornworm moths are very interesting and beautiful, by the way.

Thanks rhizo_1. I will try that :)

For future reference, you can often find what caterpillar you have if you know what it was eating. For this one, I would try searching "buttercup host plant."

(The botanical name would be better, but I don't know what buttercup you have.)

Found this page which says Ranunculus attracts American copper. Clicking the link to "American copper" doesn't show a caterpillar pic. So... searching "American copper caterpillar" brings up pics of a plain green one. So that's not it, but you get the idea, if you feel investigative in the future.

It's believed that this is the caterpillar of the White Lined Sphinx moth...one of the caterpillars where knowing the host plant won't help much! Though knowing the identification of the plant being chewed up is a HUGE clue, there are some critters, including caterpillars, that are generalists. This is one of them.

Another tricky aspect about many caterpillars, and this one in particular, is there are different color phases. (Say, did you know that our very common buddy the Tobacco Hornworm has a dark phase?)

Anyhoo, this is a caterpillar not uncommon to many different kinds of environments and found on lots of diverse plant species. It's a very large caterpillar and a big moth.

Here is a link that might be useful: White lined sphinx caterpillar

Thank you. I had searched at least 100 websites and 1000's of pictures of cats try to find what this was, so I really appreciate the help!
purpleinopp I have referenced your information for future use, thank you.
rhizo_1 that looks like the one, thank you!!!

It's sooooo hard to find an unknown insect on the web, unless you know where to begin. Purple's hint about using the name of the plant as a tool in your search is an excellent one.....I almost always ask for that information.

Just not much of a help in this case.