Great Plains Shelterbelt (en.wikipedia.org)

The Great Plains Shelterbelt was a 1934–1942 U.S. project that planted millions of trees across a broad strip of the Great Plains to reduce wind erosion and moisture loss after the Dust Bowl. It was carried out with support from agencies including the U.S. Forest Service and the Works Progress Administration, and by 1942 had planted about 220 million trees over 18,600 square miles. The article also notes that many shelterbelts have since declined in health, and that recent efforts and grants have aimed to maintain and restore them in several central Plains states.