Foxy, one of the main differences between the kankle and dulcimer is the kankle has no frets, whereas the dulcimer has frets. The dulcimer usually has diatonic frets, but some dulcimers have chromatic frets (chromatic means the frets ascend in half tones, like on a banjo or guitar).

The dulcimer had it's European beginnings as the scheitholt from Germany and the hummel from Sweeden. When these instruments arrived in America a few hundred years ago they were eventually altered and influenced the emergence of the mountain dulcimer in about the late 1800s.

In the following link to dulcimer history, it's described as basically a type of fretted zither.

For the history of the mountain dulcimer click on:
http://www.bearmeadow.com/smi/histof.htm

The mountain dulcimer is used to play folk music of various genres. Lately, some builders have been making electric dulcimers that can be used in even a rock music setting.