Complex sentence: The highest elevation is above sea level on the Kittatinny Ridge, at two areas just south of Upper Yards Creek Reservoir, west of Blairstown; the lowest point is the confluence of the Delaware and Musconetcong rivers at the county's southern tip, at of elevation.
Split into simpler sentences: The highest elevation is above sea level on the Kittatinny Ridge, at two areas just south of Upper Yards Creek Reservoir, west of Blairstown. The lowest point is the confluence of the Delaware and Musconetcong rivers at the county's southern tip, at of elevation.