As the bottleneck of intermodal transportation system has shifted from the ship/port interface to the port/inland interface, container port productivity is likely to be constrained by the connection between ports and hinterland. This study empirically explores the impacts of hinterland accessibility on efficiency of U.S. container ports. In particular, a two-stage approach is implemented. First, the container port efficiency is measured by data envelopment analysis (DEA). Then, Tobit regression analysis is undertaken to explore the relationship between the DEA efficiency scores and the ground transportation conditions, such as provision of on-dock rail facility, Class I rail services connecting to hinterland, and road congestion around the ports. The empirical results suggest that provision of on-dock rail facility at container terminals is negatively correlated with container port efficiency whilst the impacts of class I rail services are ambiguous. In general, there is a negative association between road congestion around the port and port productivity. However, this relationship tends to be negligible or even positive for primary ports of entry which enjoy substantially larger container throughput volume.