Abstract: A modular wall system for use in partitioning office, retail and other space is disclosed. The wall system includes a base which supports a wall panel. In one embodiment, the base comprises a unitary extruded beam having a web extending between a top and bottom flange and a mid-flange located between the top and bottom flanges. A plurality of cover plates cover the sides of the beam and provide a plurality of ducts for power and communications wiring. In another embodiment, the base comprises a top plate and a bottom plate, which plates are supported in parallel spaced relation by a plurality of columns. Two covers extend the length of the base and, form a rigid box structure with the top and bottom plates.