Capitol Hill is bustling with thousands of congressional staffers. Despite their numbers, and members readily admitting their reliance on these congressional aides, few scholars have turned their attention towards how lawmakers make use of their staffing resources or how these choices affect their subsequent legislative behavior and effectiveness. This dissertation seeks to quantify staff characteristics and impacts within both Representatives’ personal offices and congressional committees using two authoritative, comprehensive staff databases. More specifically, this project analyzes three unverified assumptions regarding congressional aides, their use, and their impact on Capitol Hill. The first assumption is that expertise and influence is generated solely by years of experience within congressional offices. The second is that levels of congressional staff turnover are concerningly high across House offices and that lawmakers who experience higher levels of turnover are less legislatively active and successful. The final assumption tested within this dissertation is that policy-focused aides within congressional committees are the driving forces behind various committee outputs such as facilitating committee hearings, reporting out substantive legislation, and getting it passed by the chamber. While I find that while these presumptions regarding congressional staff are generally true, they are incomplete. When assigning the most important issue portfolios to policy aides, members value higher levels of staff networking in addition to, and often above, longer tenures on the Hill; alarmingly high aide turnover is not as systemic as many observers fear, but offices that do experience comparatively high proportions of staffers departing the office are less active and successful lawmakers; and finally, committee policy staff are key in producing and getting important legislation reported out of committee, but it is more connected senior staffers who are essential in getting bills passed by the chamber. In sum, this dissertation sheds new light on how the behind-the-scenes work of congressional aides contributes to congressional behavior and legislation.