U.S. agricultural output more than doubled between 1948 and 2011, with growth averaging 1.49 percent per year. With little growth in total measured use of agricultural inputs, the extraordinary performance of the U.S. farm sector was driven mainly by increases in total factor productivity (TFP—measured as output per unit of aggregate input). Over the last six decades, the mix of agricultural inputs used shifted significantly, with increased use of intermediate goods (e.g., fertilizer and pesticides) and less use of labor and land. The output mix changed as well, with crop production growing faster than livestock production. Based on econometric analysis of updated (1948-2011) TFP data, this study finds no statistical evidence that longrun U.S. agricultural productivity has slowed over time. Model-based projections show that in the future, slow growth in research and development investments may have only minor effects on TFP growth over the next 10 years but will slow TFP growth much more over the long term.