Japanese Tree Lilac

Syringa reticulata
This tree is native to eastern Asia but is grown as an ornamental tree in North America.  It is a small tree, 20-30 ft. tall, but is the largest species of lilacs.  However, it does not seem to have the problem of powdery mildew common with lilac bushes. It grows best in full sun. The trees are noted for their fragrant, large, creamy white flowers which bloom in early June.  You can see this spectacular display in the Village along the west side of the railroad tracks.
Wikipedia, Missouri Botanical Garden