Complex sentence: From a very early period reaching beyond 1635 bands of Native Americans principally the Nipmuc tribe monopolized this region of Worcester County and the Blackstone River was once called the Nipmuc River.
Split into simpler sentences: From a very early period reaching beyond 1635, bands of Native Americans, principally the Nipmuc tribe, monopolized this region of Worcester County. The Blackstone River was once called the Nipmuc River.