Digital libraries must reach out to users from all walks of life, serving information needs at all levels. To do this, they must attain high standards of usability over an extremely broad audience. This paper details the evolution of one important digital library component as it has grown in functionality and usefulness over several years of use by a live, unrestricted community. Central to its evolution have been user studies, analysis of use patterns, and formative usability evaluation. We extrapolate that all three components are necessary in the production of successful digital library systems.