The building of the transcontinental railroads fuelled the popular idea of

Manifest Destiny

Explanation:

The doctrine of Manifest Destiny is a phrase and idea that expresses the belief that the United States of America is a nation destined to expand from the Atlantic coasts to the Pacific. This idea is also used by supporters to justify other territorial acquisitions. The supporters of this ideology believe that the expansion is not only good, but also obvious (manifest) and accurate. This ideology could be summarized in the phrase: "By the Divine or God's Authority". The phrase happened to become a doctrine over time.

4 copper and gold, the california gold rush is why im pretty sure.

julius caesar turned the roman republic into the roman empire by coming in and taking the "dictator" role during the time of a civil war (elites vs lower classes) winning battles and reputation, then declaring him dictator for life

hope this : )