For the earlier part of its history the Immigration Service's work was dominated by control of passengers at seaports and the control of crews. By the 1920s, The Immigration Service was divided into districts under the charge of an Inspector. The Immigration Officers' grade was confined to men aged over 25. Those under 25 were automatically classified as Assistant Immigration Officers. Immigration Officers enjoyed an annual salary of between £200-300 and controlled passengers and seamen at ports throughout the United Kingdom. This included Ireland until the creation of the Irish Free State in 1922 and, even after this, UK immigration officers controlled Irish ports until 1925 while the new administration made its own arrangements.