Please answer the following question: Given the following passage "Black labor played a crucial role in Miami's early development. During the beginning of the 20th century, migrants from the Bahamas and African-Americans constituted 40 percent of the city's population. Whatever their role in the city's growth, their community's growth was limited to a small space. When landlords began to rent homes to African-Americans in neighborhoods close to Avenue J (what would later become NW Fifth Avenue), a gang of white man with torches visited the renting families and warned them to move or be bombed.", answer the following question. Note that the answer is present within the text. Question: How do we know the workers were not slaves?
A:
migrants