Stalwart Securities was a proprietary trading firm located in the North Tower of the World Trade Center. (S2E11: Simon) It appeared to have at least two dozen employees, occupied at least half one floor of the building, and followed a floor plan of mostly shared desks with a few private offices for important members. The location was destroyed in the September 11 attacks at 8:46 AM, killing everyone there except Vincent Ingram and an employee named Greg who was out sick.
Anthony Corrigan's office at the firm was the physical arrival point of the first Traveler in Version One of the Traveler program: Traveler 001 took over Vincent's body between 8:40 and 8:46 AM (although his intended host was Corrigan himself). In Version Two, Grant MacLaren visited Stalwart around 8:32 AM to email the Director in 001's stead, preventing the latter from ever being sent back in time. (S2E01: Ave Machina, S3E10: Protocol Omega)