Anonymous
I second the Bradford Pear. It's by far the most common tree that flowers white in the entire US.
It also has some bad traits your tree is already displaying: its limbs grow up and to the sides in a leggy manner, just a few branches rather than nearly all, often to a weight the tree cannot sustain. The next high wind breaks off entire limbs weighing hundreds of pounds. It can damage the tree clear to the trunk, but it can also cause some pretty serious property damage, going through a roof or window, denting a car, or taking down a section of fence.
Your tree needs its top and sides trimmed this season (and probably every season).
billrussell42
close up of the leaves, flowers, and bark would be definitive. Also location.
?
Probably a Bradford Pear tree.