It was obvious that to build up a new Federal organization would require a greater period of time than was afforded by the military necessity. The existing governmental organizations of the several States presented an available substitute, and the statute authorized their use. This expedient was unprecedented, but its practice has abundantly justified its adoption. [Sidenote: State registration boards.] The immediate need was for a comprehensive registration of every male of draft age. To effect this registration each State was divided into districts containing a population of approximately 30,000, in each of which a registration board was appointed by the governor. Usually this board consisted of the sheriff, the county health officer, and the county clerk; and where the county's population, exclusive of cities of more than 30,000 inhabitants, exceeded that number, additional registration boards were appointed. Cities of over 30,000 were treated as separate units. The election district was established as the actual unit for registration in order that the normal election machinery might be utilized, and a registrar for every 800 of population in each voting or election precinct was appointed by the registration board. In cities approximating 30,000 of population, the registration board was made up of city officials, and where the population exceeded the unit number additional registration boards of three members were appointed, one a licensed physician. [Sidenote: The scheme of organization.] Governors and mayors were given considerable latitude in making geographical divisions of the States and cities for the purpose of defining registration jurisdictions; the only limitation being that approximately 30,000 inhabitants should be included within the confines of a district. The general scheme was that the board of three should exercise supervision over the precinct registrars, the governors supervising the work of the registration boards, while the mayors of cities containing 30,000 or more inhabitants acted as intermediaries between governors and registration boards. Each State was constituted a separate unit and each governor was charged with the execution of the law in his State. [Sidenote: Ten million young men register.] By proclamation of the President, dated May 18, 1917, Tuesday, June 5, 1917, was designated as registration day throughout the United States, with the exception of Alaska, Hawaii, and Porto Rico; and, due to the fact that registration organization of the States had been so quickly and thoroughly completed, about 10,000,000 male citizens of the designated ages were registered on the day set, and the first step in the operation of the selective service law was accomplished. Registration consisted in entering on a card essential facts necessary to a complete identification of the registrant and a preliminary survey of his domestic and economic circumstances. [Sidenote: Citizens carry out registration.]