Complex sentence: It flows southeastward, forming part of the boundary between the states of New Hampshire and Maine, and empties into the Atlantic Ocean near Portsmouth, New Hampshire, where it forms one of the finest natural harbors in the northeastern United States.
Split into simpler sentences: It flows southeastward, forming part of the boundary between the states of New Hampshire and Maine. It empties into the Atlantic Ocean near Portsmouth, New Hampshire, where it forms one of the finest natural harbors in the northeastern United States.