	Introduction and Methodological Notes

Although party divisions sprang up almost from the First Congress, the formally structured party leadership organizations now taken for granted are a relatively modern development. Constitutionally specified leaders, namely the Speaker of the House and the President pro tempore of the Senate, can be identified since the first Congress. Other leadership posts, however, were not officially recognized until about the middle of the 19 th century, and some are 20 th century creations. The following tables identify 15 different party leadership posts beginning with the year when each is generally regarded to have been formally established. The tables herein present data on service dates, party affiliation, and other information for the following House and Senate party leadership posts:
House Positions
1. Under this system, the Speaker—who at the time designated the chairmen of the standing committees—would name his principal lieutenant to be chairman of the Ways and Means Committee. Identifying Senate Leaders

The Senate developed an identifiable party leadership later than the House. The few existing records of party conferences in the 19 th -century Senate are held in private collections. Memoirs and other secondary sources reveal the identities of party conference or caucus chairs for some, but not all, Congresses after about 1850; these posts, however, carried very little authority. It was not uncommon for Senators to declare publicly that within the Senate parties there was no single leader. Instead, through the turn of the 20 th century, individuals who led the Senate achieved their position through recognized personal attributes, including persuasion and oratory skills, rather than the current practice of election to most official leadership posts. The development of Senate party floor leaders was one of slow evolution, like the House, but they arose for the most part from the post of conference chair. An Appendix explains the abbreviations used to denote party affiliations in this report. Leadership Posts Excluded

The tables in this report exclude some leadership posts in order to render manageable the amount of data provided. While each party's conference chair posts were the first formal party leadership positions in the Senate, eventually floor leader positions were established as uppermost in each party's leadership hierarchy. Where these have been published, they have been used as a source in this report. Party Leaders in the House of Representatives. House. Political Party Abbreviations
This report briefly describes current responsibilities and selection mechanisms for 15 House and Senate party leadership posts and provides tables with historical data, including service dates, party affiliation, and other information for each. Tables have been updated as of the report's issuance date to reflect leadership changes.
Although party divisions appeared almost from the First Congress, the formally structured party leadership organizations now taken for granted are a relatively modern development. Constitutionally specified leaders, namely the Speaker of the House and the President pro tempore of the Senate, can be identified since the First Congress. Other leadership posts, however, were not formally recognized until about the middle of the 19th century, and some are 20th-century creations.
In the earliest Congresses, those House Members who took some role in leading their parties were often designated by the President as his spokesperson in the chamber. By the early 1800s, an informal system developed when the Speaker began naming his lieutenant to chair one of the most influential House committees. Eventually, other Members wielded significant influence via other committee posts (e.g., the post-1880 Committee on Rules). By the end of the 19th century, the formal position of floor leaders had been established in the House.
The Senate was slower than the House to develop formal party leadership positions, and there are similar problems in identifying individual early leaders. For instance, records of party conferences in the 19th century Senate are not available. Memoirs and other secondary sources reveal the identities of party conference or caucus chairs for some, but not all, Congresses after about 1850, but these posts carried very little authority. It was not uncommon for Senators to publicly declare that within the Senate parties, there was no single leader. Rather, through the turn of the 20th century, individuals who led the Senate achieved their positions through recognized personal attributes, including persuasion and oratorical skills, rather than election or appointment to formal leadership posts. The formal positions for Senate party floor leaders eventually arose from the position of conference chair.
Owing to the aforementioned problems in identifying informal party leaders in earlier Congresses, the tables in this report identify each leadership position beginning with the year in which each is generally regarded to have been formally established. The report excludes some leadership posts in order to render the amount of data manageable. A bibliography cites useful references, especially in regard to sources for historical data, and an appendix explains the abbreviations used to denote political parties.
This report will be updated as changes in House and Senate party leadership positions occur.