The Pike apartment was the dwelling where the Pike family once lived.
The apartment served as the base of ops of the family.
After Evan Pike's death, Bridgit Pike became the new entry man (girl in this case) and worked for Joe and Cale Pike. She ran off on one job but was brought back to the apartment. Joe and Cale were soon incinerated by their sister, and she was fatally wounded shortly after, being brought to Indian Hill secret facility. The apartment was presumably abandoned after this.