Spring Peepers. They aren't called Hyla crucifer anymore, but I stick with the old name. They are the first musicians in the spring chorus emanating from the vernal pools, swamps, and ponds at night as soon as the ice begins to melt.
People rarely see them because they are so tiny, and nocturnal. After breeding, they leave the water as do Wood Frogs, Grey Tree Frogs, Leopard Frogs, and of course the toads.
Those two pics are Spring Peepers. They are usually grey-brown, but I have seen them turn green on a leaf.
It's worth living near a marsh in the Eastern US just for the two months of free nachtmusik from our amphibian friends. By mid-May, the toads and larger frogs will join the chorus.
Here are the frogs and toads of the Eastern US. Mostly northeastern. I've never seen a Mink Frog, but we have all of the others at the Farm. The Grey Tree frogs make a racket, but they are rarely seen because their camo on trees and bushes changes to match the bark. All you can see are their eyes.
I think it's fun to identify them all by their Spring mating calls, especially because (like owls) you rarely see them. This site gives a brief description and a recording of their individual calls.