During the First World War, the term “essential business” was used initially in military procurement, and then in disease control when pandemic influenza struck. Essential businesses were exempt from restrictions imposed in the interest of national defense or public health, so debates about essential business concerned the necessity of various goods and services to the consumer. Ultimately, the concept of essential business depended on a shared understanding of the American consumer’s rights and duties as a citizen. On the one hand, consumers furthered the state’s interests by complying with, interpreting, implementing, and enforcing public-health restrictions. On the other, what contemporaries called “the American standard of living” entitled citizens to maintain relatively large expenditures. This relationship between citizenship and consumption explains the economy’s surprising stability in 1918. The flu did not cause a depression because social norms authorized most consumer expenditures as legitimate and appropriate, even during the wartime epidemic. “Essential” work is theorized using the Marxist concept of socially necessary labor, which relates productivity and purchasing power to norms of consumption.