This chapter discusses the groundwork for extending our inquiry to a longer time frame by mapping variation in the financial subsystem over a seventy-year time span, from 1919 through 1988. Mapping the politics of the financial subsystem via a legislature-based measure presents one with an interesting dilemma: Most subsystem studies ignore the bicameral nature of Congress when developing a model of subsystem relations. The chapter explores the process of mapping the financial subsystem with an examination of the presence of interesteds on each of the banking committees between 1919 and 1988. One might suggest that if banks are interested in maintaining a policy monopoly in the area of financial regulation, they set their sights on the membership of the banking committees. Combining the chamber-based political indicators produces a Congress-based portrait of financial subsystem politics that contains several identifiable political phases. Subsystem theory recognizes that congressional committees are the key institutional building block of policy monopolies.