Every year, deep in the U.S. heartland, there's a race against nature as old as farming itself. From May to September, a group of hardworking men battle weather, machines and each other as they move south to north harvesting crops. Driving huge combines across thousands of miles, they contract work from the country's small farmers, combating hail, tornadoes, fire, mechanical trouble and total exhaustion. The new History series Harvest follows three different teams of harvesters, showing the danger and rewards of this little-known world. It's a high-stakes gamble for each team…and the people who hire them.