The story of the harmonica as we know it began in 1821 when 16-year-old Christian Friedrich Buschmann registered the first European patent for his new musical invention. His so-called "aura" was an instrument consisting of a series of steel reeds arranged together horizontally in small channels.
This initial design was widely imitated, with many modifications and advancements. Around 1826, an instrument maker named Richter developed a variation that consisted of 10 holes and 20 reeds mounted on either side of a cedar comb. His tuning, a diatonic scale, became the standard configuration of what Europeans called the "Mundharmonika" or "mouth organ."
In 1857, a German clockmaker named Matthias Hohner turned to manufacturing harmonicas full time. He introduced the harmonica to North America in 1862. By 1887, Hohner was producing more than 1 million harmonicas annually. Today, the company produces more than 90 different models, with a variety of styles and tunings.
Source: Blues in the Schools program materials and the Hohner Inc. Web site, www.hohnerusa.com