A better understanding of the lateral earth pressure in Leda clay, which is vulnerable to catastrophic landslides, would enhance the designs of retaining walls, basements, and slopes. Insights into the effects of various state parameters on the magnitude of lateral forces would be of interest. One-dimensional consolidation (loading/unloading/reloading) tests were conducted on high-quality undisturbed soil samples obtained at different depths from a site in the Ottawa region to measure the changes in lateral earth pressure with stress history. Test results indicate that soil anisotropy plays a strong role in influencing the compressibility characteristics of the soil. In addition to effective friction angle and OCR, the at-rest lateral earth pressure coefficient also depends on the level of anisotropy for sensitive Leda clays. This paper also analyzes the validity of the widely used ????0 equations in sensitive clays and evaluates its dependence on the stress history.