| The first known harmonica was patented by Christian Friedrich Buschmann in 1821. Christian was only 16, and the harmonica he invented was a simple and awkward instrument. The notes changed by a slide stick in the side, and didn't allow for too many tonal changes.
The diatonic harmonica was developed in 1826 by Richter. This version allowed for the modern 'suck and blow' method of playing, where a different note is played depending on whether a hole is being blown into or sucked on. This was called the 'mundharmonika', or mouth organ.
In 1857 the wacky world of harmonicas was changed forever when a young German whipper-snapper named Matthias Hohner turned his hand at manufacturing the instruments. He intended this ten-hole reed instrument to be used for polka music and German waltzes. In the first year, Hohner sold 650 harmonicas; mass production and an introduction to North America in 1862 meant that by 1887 over a million harmonicas were being sold all over the world.
Somewhere along the way, the name was changed from the difficult to pronounce and spell 'mundharmonika' to the simple 'harmonica', much to the relief of the English-speaking world. This occurred as a result of the harmonizing elements- it's damn near impossible to play notes on a harmonica that won't harmonize with each other. They're just built that way. It's a good thing, too, as harmonicas are annoying to listen to for long periods of time as they are- imagine if the amateur tootler was able to play bad combinations of notes as well. Ugh.
Now, over 100 years later, we can choose from more than 90 varieties of harmonica, depending on our musical needs: jazz, blues, classical, country, rock and all the genres in between.
No doubt about it, that Buschmann guy was onto something big way back then.
info from www.hohnerusa.com and "Harmonica for the Musically Hopeless" by J. Gindick, ISBN 0-932592-08-2 | 
