Simplify the following text for a Grade 12 native English-speaking person.
Original: When Europeans first arrived in North America , the Iroquois were based in what is now the northeastern United States , primarily in what is referred to today as upstate New York west of the Hudson River and through the Finger Lakes region .
Simplified: When Europeans first arrived in North America , the Iroquois lived in what is now the northeastern United States , mostly in what is today upstate New York , west of the Hudson River and through the Finger Lakes region .