Little is known about the underlying sources of gains from takeovers. Using plant-level data from the U.S. Census Bureau, I show that one source of gains is increased productivity of capital and labor in target plants. In particular, acquirers significantly reduce investments, wages, and employment in target plants, though output is unchanged relative to comparable plants. Acquirers also aggressively shut down target plants, especially those that are inefficient. Moreover, these changes help explain the merging firms' announcement returns. The total announcement returns to the combined firm are driven by improvements in target firm's productivity, rather than cutbacks in wages and employment. Also, targets with greater post-takeover productivity improvements receive higher offer premiums from acquirers. These results provide some of the first empirical evidence on the direct relation between productivity, labor, and stock returns in the context of takeovers.