Family Ranunculaceae (Buttercup Family).
A garden ornamental that has made its escape into the wild, this vine has not yet become an invasive pest here, but is fairly common now in vacant lots and other unexpected places in the city. It covers itself with little white flowers (usually four-parted, but with a fair number of five-parted variants) in late summer, with occasional blooming branches up to frost. These plants were blooming in Beechview in September.
The seeds are almost as decorative as the flowers, and well reward a close look.