Which factors did not contribute to the westward expansion of the U.S.?

The answer indicating decreased immigration as a factor that did not contribute to the westward expansion of the U.S. is accurate because westward expansion was primarily driven by an increase in immigration and migration. During the 19th century, a large influx of people came to the United States seeking new opportunities, jobs, and land, which directly stimulated the movement toward the West.

In contrast, the discovery of gold and the enactment of the Homestead Act played significant roles in encouraging westward movement. The discovery of gold in places like California led to the Gold Rush, attracting thousands of people eager to strike it rich. The Homestead Act, enacted in 1862, offered settlers 160 acres of land for a small fee, incentivizing families to move westward to establish farms and communities.

While the Cold War was a significant historical event, it occurred much later and did not impact the 19th-century migration pattern that characterized westward expansion. The context of the other factors reaffirms that decreased immigration was not a contributing factor, but rather contrary to the trends that fostered this movement across the continent.