From Native Plants PNW: 
 
Red Elderberry is native to Europe, temperate Asia, and North America.  It is found throughout most of the United States and Canada, excluding only the far north of Canada and Alaska, and the central and southern United States. It grows in moist sites; shady or open forests, streambanks, and moist clearings.
 
It is especially attractive in woodland gardens. Its vase-like, arborescent form creates an umbrella-like canopy over smaller woodland shrubs. Overgrown plants can be severely pruned.  Red Elderberry is used for revegetation, erosion control, and wildlife plantings. 
 
Deer and elk will eat the foliage, bark and buds, but Red Elderberry is usually not a preferred browse; palatability increases after frost and probably varies with relative cyanide content of individual plants.  Many birds eat the berries including thrushes, robins, grouse, and pigeons.  Squirrels, mice, raccoons, and bears also eat the fruit.  Bears will also eat the foliage and the roots.  Porcupines, mice and hares eat the buds and bark in winter. Flowers are pollinated by bees, flies, and the wind.  Fruit-eating birds and mammals disperse the seeds.
 
Primary photo credit: born1945 on Flickr (CC BY 2.0 Deed)
Secondary photo credit: waferboard on Flickr (CC BY 2.0 Deed)