The M. P. Möller Organ Company was once the largest pipe organ builder in the United States.
Operating in Hagerstown, Maryland from 1875 - 1992, Moller built over 11,730 instruments, many of which are still playing in churches, universities, and elsewhere. Probably their nearest competitor in terms of output was Wicks Organ Company of Highland Illinois, with an opus list of nearly 7,000 instruments. Wicks still exists today, though not as large an organization as it once was, having significantly downsized in 2011.