The decades following the US Civil War saw the most creative period of institution building in the history of the House of Representatives. This innovative research seeks to draw explicit links between this critical period of congressional history and the contemporary congress. The institutional practices that developed during this period, such as the development of the seniority principle and the development of the differentiated committee system loom large in the contemporary congress. Understanding the origins and early dynamics of these institutions can provide insights into the operation of the contemporary house. Specifically this project provides a comprehensive accounting of organizational change in the House of Representatives from 1870 to 1946. Data will be collected on the committee system during the period and will be augmented with data on member characteristics and on the political system more generally. When completed this research not only will shed light on congressional politics during an important and formative period of American history but also will help us evaluate contemporary political theories about collective choice.