Irish ballads like “When Irish Eyes Are Smiling” were tremendously popular in the United States at the turn of the century, but Irish music’s influence extended far beyond this genre and this period. The music carried by Irish immigrants to America found its way into popular music almost immediately following their arrival in the 1840s and 1850s. Several Civil War era songs reflect the influence, as do several cowboy songs from the American West. In fact, many music scholars argue that Irish music was the largest single building block in the formation of American country music and that it also played a part in the development of bluegrass. The Irish influence is evident, at the very least, in the heavy use of the fiddle.