Poison Sumac (Toxicodendron vernix) is a relative of poison ivy and poison oak and like those plants it contains urushiol, the chemical that causes painful, itchy rashes. While it acts like its cousins, Poison Sumac doesn't look like them. Poison Sumac is a small tree, with compound leaves, rather than a vine or shrub with "leaves of three." It grows in really wet areas-- bogs, swamps-- throughout the eastern US and Canada.
Poison Sumac's green leaves turn red in the Fall (like Poison Ivy.) Poison Sumac is not related to our common Staghorn Sumac (Rhus typhina) which also turns red in Autumn.
Poison Sumac bears white berries (or drupes) in the Fall.
I teach economics at Kalamazoo College. My wife is also an economist. We were on sabbatical in Europe for the 2014-15 academic year. (Salamanca, Spain, followed by Oxford, UK.) We were in Uruguay for the 2006-7 academic year.