1.) The historians need to describe them because they will learn something about how people build buildings, live, and interact with each other, also to gain knowledge of the past.
2.) People constantly alter the landscape of U.S. by mining, constructing roads, deforestation, and building factories that would result in pollution.
3.) Different areas have different climates and resources that is why geography has an impact on history. There are places that are inhabitable while other areas are rich in resources that people could sustain their entire lives there. The geography of a location might decide the outcome of a battle. If the area is famous for its hills and mountains, then the people will use it to its advantage and strategize a way for them to win the war. In this way, the geography and the people's actions will definitely affect the history of that area.