As the population of a civilization grows, it struggles to provide resources for the population. One of the easiest solution to this is to expand their territory in order to amass more money and power by taking the resources of others instead of producing their own.
Some expansions of territory lead to conflict but not always, there are countless ways to forge peace and harmony by sharing learning and the promise of stability by strong leaders.
Answer:
the assassination of Archduke Franz Ferdinand of Austria
The Oregon Trail was the main trail out west by settlers to Oregon and California. There are other trails that made their way out west, but not all had the destination of Oregon and California.