Which house in Congress is referred to as the upper house?

The Senate is referred to as the upper house of Congress due to its structure and the nature of its responsibilities compared to the House of Representatives, which is considered the lower house. Each state, regardless of population, is represented by two senators, resulting in equal representation among the states in the Senate. This contrasts with the House of Representatives, where representatives are allocated based on the population of each state, leading to differing numbers of representatives for larger versus smaller states.

The Senate's role includes confirming presidential appointments, ratifying treaties, and conducting impeachment trials for federal officials. This gives the Senate a significant check on presidential power and enhances its stature as a deliberative body in the legislative process, which is why it is often seen as the more prestigious chamber of Congress.