While Various research has been done about IS success factors such as system quality, information quality, and service quality in the private sector, little attention has been paid to those in the public sector, especially state or local web-based e-government systems. Meanwhile, the current practice of e-government assessments has mainly focused on system and information quality and paid little attention to service quality. This study aims to fill this gap; it validates the relationships between IS success factors and IT effectiveness, based on the case of web-based metropolitan city or provincial (state or local) e-government systems in South Korea. The result shows that not only system and information quality but also service quality have strongly significant relationships with IS effectiveness. It has practical implications for effective e-government policy development and implementation; this study suggests that current constructs of e-government assessments need to be remodeled in a way that includes service quality factor. The key contribution of this study is a theoretical and empirical foundation on which any attempt to initiate or reinforce e-government customer services can be based; this is the first empirical study to validate the influence of the service quality factor on a state or local e-government level.