This genus of 23 species of herbaceous perennials is native to North America. It was named by Carl Linaeus in honor of Professor Olof Rudbeck the Younger (1660-1740) and his father, Olof Rudbeck the Elder (1630-1702).

This group of herbaceous perennials has been a mainstay of the sunny bed or border for a long time. Most of the species are hardy for temperate zone gardens but a few tender ones are sold to be used as annuals.