"How Ya Gonna Keep 'Em Down on the Farm" is set in rural America in 1918. World War I has just ended, and America's soldiers are (hopefully) coming home.
The song features a couple—hinted to be Reuben and Rachel from the popular song of that name written in 1871—whose son has gone off to war. The couple debate what the end of the war means for their son and what he's going to do once he returns. The mother assumes that he'll come back home to the farm, but the father, Reuben, seems to know better.
The couple's plight was common to that of many rural Americans in the early 20th century. During World War I, American troops were engaged in combat for less than a year, and as a result, fatalities were light compared to those suffered by other nations. Yet the impact of the war on America's economy and society was enormous. Mobilization for the distant conflict forced policymakers to think hard about how best to meet the urgent demand for food, ammunition, and other war supplies. This led to the formation of the War Industries Board, charged with overseeing the production of all necessary goods. The work of the board was short-lived, but the lessons learned in how the government might respond to national crises by overseeing economic activity would be applied during the Great Depression and World War II.
Moral reformers jumped at the chance to secure long-pursued goals. For decades, temperance reformers had argued that alcohol ruined lives. In particular, they emphasized that it destroyed families and left women and children vulnerable. During the war, these reformers argued that temperance was a war issue. They pointed out that German Americans—suspicious characters who shouldn't be supported—owned many breweries.
More important, temperance advocates argued that the grain used to make alcohol would be better used making bread for America's fighting men abroad. These arguments were compelling within the wartime mood of national sacrifice. As a result, the 18th Amendment was adopted prohibiting the manufacture and sale of intoxicating liquor.
Other reformers seized wartime opportunities to advance their social and political agendas as well. Women, who'd been campaigning for the right to vote for years, increased their efforts, arguing that a nation willing to fight tyranny abroad should be willing to extend basic freedoms to half its own population. Congress and the president eventually responded to this argument by adopting the 19th Amendment, which guaranteed women the right to vote, in 1920.