The 118th Congress (2023-2025) is fast becoming the least productive since the 72nd Congress (1931-1933) under President Herbert Hoover at the worst times of the Great Depression.
Both the House of Representatives and US Senate are responsible for such poor performance, but clearly, if the House of Representatives is poorly organized and operated, the Senate cannot make up for it.
Both Congresses had one house Democratic, and one Republican, which also caused stalemate and gridlock.
The fact that the House of Representatives Republican majority has just voted an Impeachment inquiry against President Joe Biden, with zero evidence of such abuse of power, is a sign of how incompetent and hopeless the 118th Congress is, even with a small Democratic majority in the US Senate.
Clearly, the most productive Congresses have been when one party, in all modern times Democrats, has had a vast advantage in the number of seats in both houses of Congress.
So those most productive Congresses were, chronologically:
63rd Congress (1913-1915) under Woodrow Wilson
73rd Congress (1933-1935) under Franklin D. Roosevelt
74th Congress (1935-1937) under Franklin D. Roosevelt
89th Congress (1965-1967) under Lyndon B. Johnson
111th Congress (2009-2011) under Barack Obama
The most productive of all were the 73rd Congress under FDR, and the 89th Congress under LBJ.