Large-eddy simulation of a spatially developing shear-driven turbulent boundary layer is performed. The development of the transverse boundary layer is found to be decoupled from the streamwise flow; as a consequence, a self-similar Stokes layer develops in the transverse direction. Significant decreases in the axial skin-friction, turbulent kinetic energy and structure parameter al are observed at the junctions of the moving wall. The Reynolds stresses are drastically modified by the imposition of the shear, At the moving plate junction the additional shear disrupts the near-wall eddies, resulting in a decrease of < u'v'>, and a corresponding decrease in the production of turbulent kinetic energy, not accompanied by an analogous decrease in the dissipation. As the eddies are regenerated, however, the secondary Reynolds stress < v'w'> becomes significant, the production increases again, and the flow reaches a quasi-equilibrium collateral state, characterized by higher turbulent kinetic energy and Reynolds stresses.