This location is, predominantly, inhabited by intelligent ghouls and organized criminals. At the beginning, you note two shops and the house of the mayor - Hancock (a potential companion).
In building that you find the mayor, there also is bar Third Rail. Here, you can receive one quest from the robot bartender - Whitechapel Charlie, you can flirt with the singer and hire MacCready as your companion.
Memory Den is a place where you can receive two side quests, the longer Silver Shroud. You can also visit this location while completing main quests.
In Rexford Hotel, you can receive two quests from merchants. At the upper floor, there is a Vault-Tec representative, who will be happy to become the settler at one of your villages. You can also hire a room here, for the night.
The rest of the locked buildings are warehouses filled with villains. From the bartender you receive the quest to get rid of them.