A mix of government officials and skilled workers.
The difference between the map during the early 1900´s was the way the early settlements where shown in Irish names, portraying the fact that the Irish population was second, right under the English. Pushed out of Ireland because of religious conflict back home, decided to come to America, after they were promised land and religious freedom in return for applying their knowledge.
That is when the fear of immigrants taking over started, since English population was not that bigger than the Irish.
Since the US government is considered a republic democracy, it has many characteristics of the Roman Republic. In Rome, the officials were voted by the people. And these officials made laws and voted them. In the US government, the people vote in representatives to represent them in office. These officials vote in laws to be past, just like the Roman people did in their government.
Red River War, Battle of the Little Big Horn