Which of the following federal policies contributed to the growth of suburbs in the United States during the 1950s?

The construction of interstate highways played a pivotal role in the growth of suburbs in the United States during the 1950s. This extensive highway network facilitated easier and faster commuting between suburban areas and urban centers, making it feasible for families to live outside of city limits while still having access to jobs, shopping, and entertainment in the city. The highways not only improved accessibility but also spurred economic development in suburban areas, leading to increased residential construction and the establishment of new communities.

By contrast, the other options, while relevant to urban development and public welfare, did not directly influence suburban growth in the same significant manner. Legislation prohibiting housing discrimination, for instance, aimed at combating segregation and ensuring equal access to housing rather than directly promoting suburban expansion. Improvement of mass transportation systems, although beneficial, often focused on urban transit rather than the suburban sprawl that was characteristic of the 1950s. Lastly, funding for parks and public recreation areas enriches community life but does not inherently drive the suburbanization phenomenon like the highway system did.