It is a Bradford pear tree.
It stinks when it blooms and has nasty little fruits that are supposed to be barren--but it keeps trying to grow little trees in the lawn!
I despise Bradford Pears. The show in the Spring is nice, I suppose, as is the red/purple color in the fall, but the shape is unnatural and the branching structure is a horrendous mess. In addition, they are grafted, and whatever the rootstock is, if it sends up shoots, they are ferociously spiny. Plus, the wood is ridiculously brittle. When they get about 30-40 feet tall, they start shedding great chunks; I have seen whole treetops on the ground after a summer thunderstorm. For the life of me, I can't understand their popularity!