A community computer network facilitates civic participation by providing pervasive local resources online and by connecting people to local communication and discussion channels, public and non-profit organization leaders and members, and many other civic resources. We present findings from longitudinal data (two rounds between 2001 and 2002) of a stratified random survey of 100 households in a mature community network, the Blacksburg Electronic Village (BEV). We offer exploratory and confirmatory analyses, including a 'civic effects' model, that show demographic characteristics (education, age) and psychological factors (extroversion) explain staying informed, collective efficacy, group membership, activism, and using the Internet for civic and political purposes. The model further explains differences in respondents' involvement in local issues once they go online. Informed activists with multiple group memberships become more involved in local issues once going online, whereas informed non-activists become less involved once online. Our study suggests that in order to play a constructive role in creating a more civil society, community networks should explicitly pursue strategies that encourage community activism. One way to do this, given the strong role of association membership in activism, is for ISPs to offer bundled standard Internet applications at low cost to non-profit community groups (e.g. email for leadership, online discussion for members, web space). Community networks should also promote and support the use by local groups of innovative tools for non-experts, such as easy collaborative web-based tools for information production and collaboration.