We discuss the design, implementation and evaluation of two related visualizations of authors? activities in Usenet newsgroups. Current Usenet news browsers focus on messages and thread structures while disregarding valuable information about the authors of messages and the participants of the various discussions. Newsgroup Crowds graphically represents the population of authors in a particular newsgroup. Authors are displayed according to the number of messages they contribute to each thread and the number of different days they appear in the space, illustrating and contrasting the interaction patterns of participants within the newsgroup. AuthorLines visualizes a particular author?s posting activity across all newsgroups over a period of one year. This visualization reveals temporal patterns of thread initiation and reply that can broadly characterize the roles authors play in Usenet. We report the results of a user study that explored the value of these interfaces for developing high-level awareness of the activity and population in these conversational spaces. We suggest that interfaces that convey information about the social histories of populations and individuals may support better selection and evaluation of newsgroup content.