Complex sentence: As the City of Brooklyn grew, the area south of Atlantic Avenue (known as "South Brooklyn") began to become built-up, but lacked easy access to the ferry terminals in the northern parts of the city of Brooklyn.
Split into simpler sentences: As the City of Brooklyn grew, the area south of Atlantic Avenue, known as "South Brooklyn," became developed. However, this locale lacked easy access to the ferry terminals in the northern parts of the city of Brooklyn.