Electricity transmission lines constitute a vital element in any electrical power system. Nevertheless, the progressive collapse of these structures caused by accidental events and cascade failure can lead to a wide range of failures, including total collapse. The failure of power transmission line structures due to extreme wind and ice loads poses a substantial challenge for electrical power distribution companies globally. In this study, the progressive collapse behavior of a 230-kV electrical power transmission line in Fars Province, Iran was evaluated utilizing the alternative load path method within a nonlinear dynamic analysis framework. Finite element models of a tangent electricity tower (DC0), a terminal tower (DC90), and the conductors of the transmission line were created and simulated using SAP2000 software. The investigation focused on the impact of removing the legs of the transmission tower, and the simulation analyzed the progressive collapse behavior under various loading conditions, including wind load, snow-induced freezing, and simultaneous wind and ice load. By employing the nonlinear dynamic analysis of the progressive collapse, the stresses developed in the structural elements were evaluated, and the damaged elements were identified. The results demonstrated that following the failure of one leg, the tangent and terminal towers remained stable under gravitational loads. However, under extreme winds at a 90∘ angle, the failure of a leg resulted in significant damage to the towers. Further assessment of the tangent and terminal towers revealed that the terminal tower exhibited higher strength compared to the tangent tower. This was evident in the lower dispersion of displacements and a reduced number of damaged elements observed in the terminal tower when one leg was removed.