Beginning with publication of Toward Understanding 19th Century Congressional Careers: Ambition, Competition, and Rotation in 1977, I have been interested in mapping and accounting for the emerging career structure of 19th and early 20th century politicians and assessing its implications for America's political development. After touching upon these issues in Strategy and Choice and more recently in Congress and America’s Political Development: The Transformation of the Post Office from Patronage to Service, I have returned to a more direct investigation of congressional career development. My current work concentrates on the choices of House and Senate incumbents to seek reelection, to retire from public office or to move to some other office. This research involves analysis of ICPSR's 7903, Biographical Directory of US Congress, file. So far I have identified and addressed two deficiencies in these data. First, although birth dates were used to construct a variable, age at entry, both years of birth and death were inexplicably omitted from this file. Working with name files kindly supplied by the Senate Historian's office, I have merged these data (with about a 1 percent failure rate). These large excel files are available on request. Second, the ICPSR data set is ambiguous in classifying departures from Senate under indirect elections. Checking the codes for "reasons for leaving" in variable 83 against summaries of state legislative elections of senators reported in annual issues of the Tribune Almanac revealed a number of discrepancies (see changes in v83).