Context: 114th Street marks the southern boundary of Columbia University’s Morningside Heights Campus and is the location of Butler Library, which is the University’s largest.

Question: Which library is Columbia University's largest?
Answer: Butler Library

Question: 114th Street marks the southern boundary of which university's Morningside Heights Campus?
Answer: Columbia University

Question: 114th Street runs along which boundary of Columbia University's Morningside Heights Campus?
Answer: southern