During the last two years of World War I, almost 24 million Americans were required to register for the military draft. I must emphasize civilian registration because only a small minority of these men was ever inducted into the military. A higher percentage of this American male population was reached by this process than by the 1920 census. In addition, the information provided was much more complete and reliable than the census information because the registrant was the person providing the information. Because many states did not have birth registration during the years these men were born, the cards serve the function of substitute birth records.  - Ray H. Banks