History is the knowledge and study of past events. History can also be known as the past events and activities that happened to a subject of discussion. For instance, the History of the United States or the History of the Democratic party.
The text speaks of the Civil War which is a past event so when talking about it in relation to the era it occured, you are speaking to the historical context of that era.
Answer: "What surprises me", she said, "is not that con artists exist, but that enough people would have been both wealthy and gullible enough to think that they could buy the Brooklyn Bridge".
