Final answer:
Increased migration to cities during the early 20th century had various effects, including worsening living conditions and sanitation, increasing political power for political machines, and the creation of settlement houses. However, the declining availability of unskilled workers was not a result of this migration.
Step-by-step explanation:
Increased migration to cities during the early 20th century had several effects, but one effect that was not a result of this migration was the declining availability of unskilled workers. In fact, the influx of immigrants into cities often increased the availability of cheap labor. However, the effects of increased migration did include worsening living conditions and sanitation, as the overcrowded cities struggled to provide adequate housing and infrastructure for the growing population. Additionally, the political power of political machines increased as they capitalized on the needs and vulnerabilities of the immigrant population. Lastly, the creation of settlement houses was one positive outcome of increased migration, as these institutions provided social services and support to new immigrants.