The Burwell-Morgan Mill, established in 1785, is the oldest operable merchant mill in the Shenandoah Valley. In the mid-nineteenth century the mill operated twenty-four hours a day, seven days a week, processing more than sixty thousand bushels of wheat per year. The community of Millwood grew around this commercial center as related businesses were established, and by way of the seaports at Alexandria and Baltimore, mill products were shipped abroad.

The RMSL is at the grade crossing of post office history with railroad research. It focuses upon how mail was distributed in Railway Post Offices between 1864 and 1977.