It’s quite possible that the first harmonica was invented by the plucky creative Chinese. Hell they created everything else. That said, it wasn’t until a German clockmaker, Matthias Hohner, invented the harmonica.
That was 1857. And when it came to the United States, it grew into a wild popularity. And so those movies and TV shows that always has a harmonica on the skirmish lines of Civil War battles, well, they are wrong.
The US had a shaky trade relationship with Germany. So to secure distribution over the North Atlantic would have required firm contracts and many more harmonica in existence.
Only about 50,000 were made in the first ten years in Germany. :
That said, enjoy.