Final answer:
The region known as the North, particularly the Midwest and the Great Plains, benefited from agricultural and transportation advances to supply grain. This area included states like North Dakota and developed significant infrastructure, like railroads, to support its role as a major food-producing area.
Step-by-step explanation:
The region that benefited from advances in agriculture and transportation to harvest mass grain efficiently to feed growing cities is the North, specifically the Midwestern states including areas like the Great Plains. This region, often called "King Wheat," saw the development of cities such as Chicago, which became central to the agricultural industry.
Advances during the Industrial Revolution in the 1820s and beyond saw this region's infrastructure grow with extensive railroad grids that enabled the efficient movement of agricultural products. Over time, as the farms in the Midwest became increasingly mechanized, the production of foodstuffs like wheat and corn scaled up significantly to feed not just local populations but also to supply during the Civil War and beyond.
Harvested grain from the fertile soils of the Midwest, such as in states like North Dakota, contributed to the Midwest's reputation as a major food-producing area. The changing economics of crops like soybeans, corn, and wheat has influenced the farming patterns in this region, with shifts occurring in response to crop prices and agricultural conditions, such as the dryness west of the 100th meridian which makes wheat a more suitable crop than corn or soybeans.