To promote the penetration of electric vehicles (EVs), a charging facility (CF) planning model based on Yen's algorithm is proposed for coupled transportation and distribution systems (DSs) considering traffic congestion. This model not only takes into account the influence of new CFs on the power system but also considers the impact of CF locations on traffic flow distribution and congestion level in the transportation system (TS). Yen's algorithm is innovatively employed to offer multiple possible choices for EV drivers' route selection considering CF locations determined in the traffic flow assignment model. Overall, the total cost of both distribution and TSs is minimized to obtain the optimal CF planning results. For the DS, generation cost, energy loss, and penalty cost for voltage deviation are included. For the TS, the main objective is to ensure EVs can reach their destinations at the lowest cost, while the travel time due to different path selections and the delay time caused by congestion can be minimized. Finally, a comprehensive case study on the integrated IEEE 30-bus and a 25-node TS is conducted to validate our approach.