A pair of groundbreaking documentaries from director Pare Lorentz leads off with "The Plow That Broke the Plains," a government-sponsored look at how the uncontrolled plowing of the Midwest led to the Dust Bowl. Then, produced by the U.S. Farm Security Administration, Lorentz's acclaimed documentary "The River" looks at the history of the Mississippi River, the farms and industries that grew along it, and how years of misuse led to flooding and other disasters in the '30s. A moving early example of the documentary's use as social propaganda. 60 min. total. Standard; Soundtrack: English.