To a large extent, the minority leader's position is a 20th-century innovation. Prior to this time congressional parties were often relatively disorganized, so it was not always evident who functioned as the opposition floor leader. Decades went by before anything like the modern two-party congressional system emerged on Capitol Hill with official titles for those who were its official leaders. However, from the beginning days of Congress, various House members intermittently assumed the role of "opposition leader." Some scholars suggest that Representative James Madison of Virginia informally functioned as the first "minority leader" because in the First Congress he led the opposition to Treasury Secretary Alexander Hamilton's fiscal policies.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Who was Treasury Secretary at time of first congress?
Alexander Hamilton