TaStahl said: I've never noticed it actually getting 'cottony', but will definitely keep my eyes out for that this spring.
Eastern Cottonwoods are dioecious, meaning each tree has either male or female flowers, not both. If your tree is male, it wouldn't produce the cottony seeds that cottonwoods are famous for.
For what it's worth, it does appear to be Eastern Cottonwood. Beautiful trees when they reach that size, aren't they?