Great plains will likely provide the best farmland. Option three is correct.
The Great Plainsrefers to the broad expanse of flat land (called plain), much of it covered in prairie, steppe, and grassland, that is located west of the Mississippi River tallgrass prairie in the United States and east of the Rocky Mountains in the U.S. and Canada.
It involves:
The entirety of the U.S. states of Kansas, Nebraska, North Dakota, and South Dakota
Parts of the states of Colorado, Iowa, Minnesota, Montana, New Mexico, Oklahoma, Texas, and Wyoming
The southern portions of the Canadian provinces of Alberta, Manitoba, and Saskatchewan