Final answer:
The advertisement is most closely related to the Pacific Railway Act, which facilitated western expansion in the United States.
Step-by-step explanation:
The advertisement in question is most closely related to the Pacific Railway Act, which was a significant piece of legislation passed by Congress in 1862 to facilitate western expansion in the United States.
The Pacific Railway Act granted generous funds to two companies, the Union Pacific and the Central Pacific, to build a transcontinental railroad, enabling the movement of people and goods across the country.
This Act was a crucial step taken by the U.S. government to help Americans fulfill the goal of western expansion.