Definitely voting on an American Bullfrog (Rana Catesbeiana) here. If not, probably a similar species such as the Green Frog (Rana Clamitans).

Keeping a large Ranid such as an American Bullfrog will require a lot of work and money, along with a sizable tank for when the frog reaches adulthood. These frogs grow to the size of dinnerplates, and with an appetite to match. However, don't be discouraged by this; these frogs make fun, entertaining, comical, and unique pets.

If you want, I can give you a brief overview of how to care for an American Bullfrog, as well as the tadpoles/metamorphs. I keep two young adult male Bullfrogs myself.