A remarkable set of shore-oblique sand ridges occupies the inner portion of the storm-dominated Middle Atlantic and South Atlantic Bights, off the east coast of the United States of America. A mechanism for present-day formation and growth of these distinctive geological features follows from a linearized analysis of the stability of alongshore-periodic topographical perturbations, based on a depth-averaged fluid dynamical model with a simple representation of sediment transport. The analysis indicates exponential growth of shore-oblique features as a result of offshore deflection of storm-driven alongshore flows at ridge crests, which leads to a convergence of sediment flux because the effective carrying capacity decreases with increasing distance offshore. The analysis indicates a set of conditions required for ridge growth. Model solutions for topography under conditions favorable for ridge growth are strikingly similar to the observed sand ridges. ¿ American Geophysical Union 1995