The invention of the cotton gin in the 1790s allowed the cultivation of short staple cotton, which could be grown in much of the Deep South, where warm weather and proper soil conditions prevailed. The industrial revolution in Europe and New England generated a heavy demand for cotton for cheap clothing, which caused an exponential demand for slave labor to develop new cotton plantations. There was a 70% increase in the number of slaves in the United States in only 20 years.