The American elm is one of the most beloved native American trees. In years past, it was used overwhelmingly as a shade tree and street tree because of its graceful, arching, vase-like growth form, which meant that it formed a high, spreading canopy with open air space beneath, and the cross-grained wood gave strength to the branches that meant that it didn't break apart easily.
However, the Dutch elm disease devastated the American elm, causing catastrophic die-offs in cities across the nation. Once this fungal disease infected one tree on a street, all the other trees close to it would quickly die because the fungus would infect them via the roots through root grafts that the tree would form. There still are many American elms in the woods, but in cities, the ones that survived were generally ones that were isolated from other elms.
Such cities as Kansas City, Missouri, had used mostly American elms in planting its city streets, and had some of the best-shaded residential streets in the nation -- until the disease almost obliterated these plantings in the late 1960s and early 1970s.
Attempts have been made over the last few decades to breed disease-resistant elms. The Liberty elm is one example of such a strain.
Other trees that have been used as substitutes for American elms are Zelkova and Chinese elm.