Final answer:
Levittown was built on farmland in Long Island, New York, and comprised a planned community of 17,000 homes.
Step-by-step explanation:
The mass of land that Levittown was built on was part of farmland purchased on Long Island, New York, by William Levitt for the purpose of creating a planned community. This development, known as Levittown, was one of the first and largest suburbs in the United States, ultimately consisting of 17,000 homes. Utilizing innovative mass-production techniques, Levitt transformed this area into a model suburb, significantly impacting housing development in the post-war era.