This article discusses a worldwide epidemic--a pandemic--that appeared in the United Sates during the latter part of the summer of 1918. During 1918 and 1919, between 50 and 100 million people around the globe fell victim to a rapidly spreading and untreatable strain of influenza. The pandemic so severely affected the U.S. population that roughly 675,000 Americans died and more that 25% were infected. Within months, the flu had killed more people than any other illness in recorded history. Here, the authors feature documents related to the flu pandemic of 1918, which include the letter from B. M. Holden to Col. L.A. Nicolson in Washington, D.C., illustrating the extent of the outbreak, and offer teaching suggestions for social studies teachers in discussing the terms "epidemic" and "pandemic." (Contains 3 notes.)