Final answer:
The answer to the question is a union shop. This requirement for union membership upon employment has been a contentious issue in labor history, with debates surrounding the American Plan and the shifting landscape of American labor with declining union membership.
Step-by-step explanation:
Union shop is the correct answer to the question of a place of employment where the employee is required to join the union within a specified number of days after being hired. In the context of American labor history, the concept of a union shop played a significant role in shaping labor relations. The American Plan was a campaign by antiunion industrialists to promote the ideal of an open shop, which allowed workers the freedom to choose whether to join a union, as opposed to a closed shop, which required union membership as a condition of employment. Labor unions have been a crucial aspect of the American workforce, especially in industries like the automobile sector, where organizations like the International Union, United Automobile, Aerospace and Agricultural Implement Workers of America (UAW) represented the workers. Union membership in the U.S. has experienced a significant decline from its peak during the mid-20th century, and this shift reflects broader economic transformations from manufacturing to service industries, as well as employer resistance to labor unions.