Complex sentence: Route 99 is a north-south state highway in the U.S. state of Massachusetts, connecting the North End neighborhood of Boston with U.S.1 north of Boston in Saugus.
Split into simpler sentences: Route 99 is a north-south state highway in the U.S. state of Massachusetts. Its southern terminus is in the North End neighborhood of Boston, and it proceeds north to U.S.1 in Saugus.