The implementation and construction of Mechanically Stabilized Earth (MSE) walls has undergone substantial expansions in recent years, owing to its relatively low cost, ease of construction, and high efficiency compared to conventional retaining methods. As a result, MSE walls are being constructed to greater heights with complex features (e.g. multiple tiers, equivalent batter angles, close reinforcement spacing) even though impacts on wall response associated with these characteristics are not well understood. Available methods to predict wall responses are limited to empirical databases of single tiered walls less than 20 m and designers are left to complex finite element modelling to estimate the behavior of tall walls (walls with heights greater than 20 m). The current study aims to provide practitioners with a better understanding of the working stress behavior of tall MSE walls during and after construction through the use of a calibrated numerical model that incorporates pressure dependent soil, panel-soil interaction, non-linear soil reinforcement interaction, facing rigidity, foundation stiffness, and compaction stresses. First, an extensive laboratory investigation is conducted to characterize the plane strain and three dimensional stress-strain and stress-dilatancy response of a well-graded gravelly soil. Laboratory pullout tests are performed to characterize the influence of reinforcement spacing on load-displacement response. Results from the high quality laboratory investigations are used to calibrate specific numerical elements in FLAC (e.g. reinforcement-soil interface, facing-soil interface, soil constitutive response) incorporating pressure dependent constitutive responses. A numerical model representing a 46 m tall MSE wall is developed in FLAC, incorporating calibrated element parameters. Measurements made during the construction of a 46 m tall MSE wall are used to establish those factors within the model that most accurately simulate the observed wall performance. Results from a geometric parametric study conducted to assess the influence of boundary conditions on wall response are presented, focusing on impacts associated with tier height, tier offset, and wall height. The synthesis of the results from the geometric parametric study are used to establish a more thorough understanding of wall response, with specific emphasis on wall displacements and reinforcement strains.