Questions about the characteristics of Members of Congress, including their age, education, previous occupations, and other descriptors, are of ongoing interest to Members, congressional staff, and constituents. Some of these questions may be asked in the context of representation, in efforts to evaluate the extent to which Members of Congress reflect their constituencies and the nation at large. In other instances, questions arise about how the characteristics of Members have changed over time, which may speak in part to the history of Congress. This book provides profiles of Senators and Representatives in selected Congresses since 1945, with a focus on service tenure and patterns of member service.