The principles of trade unionism are based on working people acting together in solidarity with each other, to improve wages, working conditions, and life for themselves and all others. In its most developed forms, this extends not only to the worker next to you, but to working people all around the world, wherever they might be. Some of the foremost proponents of these principles in the United States since the 1880s has been the American Federation of Labor (AFL), then later the Congress of Industrial Organizations (CIO), and since their merger in 1955, the AFL-CIO.