In fact the agricultural devastation helped to lengthen the Depression whose effects were felt worldwide. ... Poor agricultural practices and years of sustained drought caused the Dust Bowl. Plains grasslands had been deeply plowed and planted to wheat.
Do you mean the width of the Dust Bowl? Because if so the diameter of the dust bowl wasn't exact but the Dust Bowl was touched by almost 12 state from the Texas panhandle to North Dakota and Southeastern of Montana.