Rowan is European mountain ash (Sorbus aucuparia). It has been traditionally used for bows in Europe. We have a couple of closely related species in North America: Northern mountain ash (Sorbus decora) grows in the northeastern/north central US and Canada. American mountain ash (Sorbus americana) has much the same range except that it grows through the Appalachians south to Georgia at higher elevations. Here in western NC, it's pretty common above 5,000' elevation or so. Greene's mountain ash (Sorbus scopulina) grows thoughout many of the western states from Alaska to New Mexico, and western mountain ash (Sorbus sitchensis) grows in the Pacific Northwest. The true European rowan is sometimes planted here as an ornamental tree, and is naturalized in some of the northern tier of states. As far as how good our native mountain ashes are for bows, couldn't tell you, but I'm on the lookout for a nice straight mountain ash to try.