Quercus phellos IDed by long, oblong leaves, usually stiff, with prominent midribs; smooth leaf margins that tuck slightly down; gray crusty bark with relatively smooth, light gray branches; light green new growth with white lenticels. I found it quite hard to ID this tree in the winter, but the leaves give it away. The bark is actually very distinct, especially at the age of most of the NYC willow oaks: it tends to be really rough and brownish at the base and becomes smoother and grayer a little further up.
The leaves look like willow leaves but they are not serrate and their tips have short bristles