The pink bark (between the rough gray plates, 5th photo) on the lower trunk points to River Birch (Betula nigra), but the normal leaf seen on the 3rd photo does not appear to show the rhombic (diamond-shaped) outline for that species (but perhaps the leaf is young and has not assumed its mature form). The pistillate flower cluster (female "cone", 4th photo) is developed with this spring's leaves, which is also consistent with River Birch. Abigail, if you could provide a photo showing the color and pattern of the peeling bark higher up on the trunk (or describe from memory if returning to the tree is not convenient), it would help to clinch the tree ID.

I see Charley just identified the insect as the Spiny Witch Hazel Gall Aphid, which uses river birch as an alternate host. I meant to get back to this posting sooner with my "best guess" that the tree was indeed River Birch; there is a good photo of the rough, pinkish bark that forms on the lower trunk of large stems of this tree species on the University of Connecticut Plants Database webpage (click on the first thumbnail for "Bark" in the left column). Also, some of the leaves in the defocused background of Abigail's photo do show the characteristic rhombic shape.