It's probably a medium-sized mammal. It's not a canid (fox, coyote) or a feline (bobcat, mountain lion), because they have four toes instead of five.
Opossums have five toes, but their "big toe" on the hind foot sticks out almost perpendicular to the rest. Raccoons have five toes, but they have very long, distinctive digits that produce a hand-like pattern.
So now I'm wondering about the mustelids, or weasel family. It's large, so not a skunk. It isn't webbed, so not a river otter. The claws are prominent and strongly curved inward — could it be an American Badger (Taxidea taxus)?
If you have a guess or notice different things about these tracks, let me know. I'll post any further updates.