The most active Congress, as measured by the number of bills passed into law, excluding private bills, was the 84th (1955-1956) which passed 1,028 bills. Eisenhower (R) was President; Lyndon Johnson (D) was Senate Majority Leader and Sam Rayburn (D) Speaker of the House. The least active was the 112th (2011-2012) which passed 238 bills. The current 113th Congress is on a pace to pass just 70!
Source: Elliot F. Eisenberg, Ph.D.