But production in the United States is declining, according to the Department of Agriculture. Land devoted to fresh tomato production in Florida, a major producer, has fallen to around 30,000 acres, down from 39,400 acres at the start of the century, according to the agency. Similar reductions have occurred in California, North Carolina and other states.

Mr. Webb, the son of a Kentucky machinery dealer who was raised in nearby Lexington, said he always planned to build something big in Kentucky. Years of research, and the state’s abundance of land and water, drew him to agriculture.

This colossal plot in Morehead is only the first step in Mr. Webb’s ambitious plan. The next is to be so successful that other greenhouse growers follow AppHarvest to the state.

His hope, he said, is to rejuvenate the state’s economy, devastated by the collapse of the coal industry, with a “sustainable produce hub” that would turn Kentucky into “the agtech capital” of the United States. Mr. Webb also plans to build huge AppHarvest greenhouses in other eastern Kentucky communities.

That goal is achievable. Greenhouses provide a controlled environment that allows vegetables to be grown year-round. Tomatoes grown in greenhouses accounted for 32 percent of the domestic supply in 2017, the latest year for accurate figures, according to a report published in March by the Agriculture Department. The same year, Kentucky farmers grew tomatoes in 1.1 million square feet of greenhouses on more than 300 farms.