The great earthquake sequence that occurred in the central Mississippi River Valley during the winter of 1811--1812 is unprecedented in the historical record of seismicity within stable continental plate interiors. We show, using viscous flow models based on high resolution seismic tomography, that the descent of the ancient Farallon slab into the deep mantle beneath central North America induces a highly localized flow directly below the New Madrid seismic zone (NMSZ). This localization arises because of structural variability in the Farallon slab and the low-viscosity of the sub-lithospheric upper mantle, and it represents a heretofore unrecognized and possibly significant driving mechanism for the enigmatic intraplate seismicity.