Complex sentence: When it was founded the Lake Itasca region was able to claim that it was the juncture of the three great habitats of North America: the Great Plains, the Deciduous Forest of the south, and the Coniferous Forest of the north.
Split into simpler sentences: When it was founded the Lake Itasca region was able to boast that it was the juncture of the three great habitats of North America. The Great Plains, the Deciduous Forest of the south, and the Coniferous Forest of the north.