1. I am a cartographer (these days known a a G.I.S. dude).
2. As important in studying cartography is studying the history of surveying. They actually had surveyors survey barely inhabited portions of the west in the mid-1800's, placing stakes in trees in the wilderness, taking measurements with chains and doing a pretty darn good job of it given the crude tools they were using.
Regarding the Americans Indians,
recent genetic research has determined that about 1/3 of the genes of American Indians come from from West Siberians, not East Siberians as is usually believed, which would put them closer to modern Europeans in lineage than modern East Asians. That might explain the apparent closeness of some tribes to customs and craftsmanship of some Europeans. But bear in mind this lineage goes back farther than what we now consider modern Europeans to look like. This was all before blond hair and the like evolved.