The Federation is divided into five departments, representing the most important groups of labor: the Building Trades, the Metal Trades, Mining, Railroad Employees, and the Union Label Trades. ¹ Each of these departments has its own autonomous sphere of action, its own set of officers, its own financial arrangements, its own administrative details. Each holds an annual convention, in the same place and week, as the Federation. Each is made up of affiliated unions only and confines itself solely to the interest of its own trades. This suborganization serves as an admirable clearing house and shock-absorber and succeeds in eliminating much of the friction which occurs between the several unions. ¹ There is in the Federation, however, a group of unions not affiliated with any of these departments. There are also forty-three state branches of the Federation, each with its own separate organization. There are annual state conventions whose membership, however, is not always restricted to unions affiliated with the American Federation. Some of these state organizations antedate the Federation. There remain the local unions, into personal touch with which each member comes. There were in 1916 as many as 647 "city centrals," the term used to designate the affiliation of the unions of a city. The city centrals are smaller replicas of the state federations and are made up of delegates elected by the individual unions. They meet at stated intervals and freely discuss questions relating to the welfare of organized labor in general as well as to local labor conditions in every trade. Indeed, vigilance seems to be the watchword of the Central. Organization, wages, trade agreements, and the attitude of public officials and city councils which even remotely might affect labor rarely escape their scrutiny. This oldest of all the groups of labor organizations remains the most vital part of the Federation.