In all of US history, which Congressional marjority/minority leaders and speakers are considered historically important? For example, FDR and Lincoln are, for better or worse, considered historically important Presidents.
Probably the most famous and historically significant US Congressional leader was Henry Clay, who was a dominant, if not the dominant leader of the early 19th Century Congress. He was the founder and leader of the Whig party (one of the two main parties of the era), and was the driving force behind The Missouri Compromise and (as a Senator) The Compromise of 1850, both of which for a time defused major pre-Civil war Slavery crises.
The role of Speaker regained a lot of power in the mid 20'th Century under Sam Rayburn, but never really the same stature. During part of his tenure, his protege Lyndon Johnson asumed similar control of the Senate, producing a fairly imposing legislative partnership.