Center of population moved past the Alleghains. Fur-trapping used the rendevous system. Ecological Imperialism expoliated the stock in the West. There was an influx of immigrants from Ireland and Germany. The Irish were escaping famine and the Germans were escaping autocracy. Nativists disliked the foreigners. Know-Nothing Party formed against the foreigners. 1. What were some obstacles pioneers faced? 2. What is Ecological Imperialism? 3. What were the major cities in the U.S. by the mid 1800?s?