Final answer:
In the context of free labor ideology, slave labor threatened Northern White wage laborers and free farmers by creating competition that could lower wages and by monopolizing the best agricultural land, making it difficult for free farmers to find and make use of land.
Step-by-step explanation:
According to free labor ideology, the economic interests of Northern White wage laborers and white free farmers were threatened by slave labor in two main ways. First, there was the concern over competition for jobs and lower wages, as employers might prefer the unpaid labor of slaves over paying wages to free labor. This could result in fewer available jobs for wage laborers and potentially depress wages where free labor was used. Secondly, the prevalence of slave labor could lead to limited access to resources and land for white free farmers. The extensive plantation system of the South relied on slave labor, which in turn monopolized the best agricultural land, reducing opportunities for free farmers to own and work their own land successfully.