Bower Book Cover Bowers' Standard Method for the Violin. Chicago: Sears, Roebuck and Company, [c. 1891].
Pictured above is "The Bower Book", which was a standard tutor sold and distributed by Sears, Roebuck & Company of Chicago.  Generally, when a violin was sold by mail order to someone out in rural America, the violin was sold as an outfit and included with this outfit was an instructional book such as this. 

It's not much a leap to think that at least of melodies presented in these tutorial books might have wormed their way into local fiddle traditions.  Even if the fiddler couldn't read there might be someone in the house who could play the piano or reed organ and read the music.  I've heard several anecdotes from old fiddlers to this effect, that they learned tunes by way of their daughter playing them on the piano so they could learn them by ear.  

The picture of the cover above is linked to an excerpted copy of the book.  You can review the table of contents and see a few examples of the tunes in this collection.  Titles include: