I found this caterpillar in my garden, is that a good thing?
The caterpillar is the larva (youngster) of one of Oregon's swallowtail butterflies, in the family Papilonidae. It may be the Pale Swallowtail, Papilion eurymedon.
If you still have the caterpillar, consider rearing it to the adult stage, when the identification should be easy to verify. Finally, release the butterfly so it can find a mate.
To rear a caterpillar to the adult stage, use these directions.