Ironweed, or New York ironweed, is a native perennial in the aster family blooming in late summer and early fall.  There are several species,  difficult to tell them apart.

New York ironweed occurs in wild moist thickets, along streambanks from Massachusetts to Mississippi. It is a tall, and coarse upright perennial. The botanical name is Vernonia noveboracensis. The composite flowers are deep purple and have numerous tiny, fluffy, terminal clusters (cymes). Flowers give way to rusty seed clusters in fall. The common name has varyingly attributed to certain "iron-like" plant qualities including the tough stems, the rusty-tinged color of fading flowers and the rusty colored seed that develop.

The name honors William Vernon d.c. 1711, an English botanist who collected in Marland in 1698. The specific epithet means of New York.
 

Hope this helps.