The boundary of the Martian crustal dichotomy in the eastern hemisphere is one of the most striking topographic features on the planet. The long wavelength topography of much of the boundary is expressed by a broad rise and an arched ramp that slopes downward from the southern highlands into the northern lowlands and often ends in a steep scarp. Lithospheric flexure of the southern highlands for both a continuous and broken plate boundary with the northern lowlands lithosphere is modeled. We find that the long wavelength topography of the boundary is best fit by a lithospheric deflection profile of a broken lithosphere for reasonable values of the flexural parameter. The lithosphere near the dichotomy boundary may have been weakened by tectonic stress associated with the formation of the crustal dichotomy by subcrustal transport caused by overturn of an early magma ocean.