First up — Dr. Robert Ford.
Ford is Westworld's park director and one of its co-founders. The process for creating and programming the hosts is all based on his team's original research conducted over 30 years ago. Ford has the highest level of control over the narratives, design, and coding for the robots.
Arnold is Ford's original partner in the parks.
We saw this photo of a younger Ford and Arnold in episode three, when Ford was telling Bernard about the other co-founder of Westworld. Arnold allegedly killed himself inside the park right before it opened over 30 years ago.
Bernard Lowe is the Head of Behavior and a programming specialist.
Lowe appears to be Ford's right-hand man — the two often discuss the hosts and their coding updates. Bernard had a young son, Charlie, who died of unknown causes. He video chats with his (possibly) ex-wife, and is engaging in an affair with Theresa Cullen.
Theresa Cullen is the Head of Quality Assurance,
It's Cullen's job to make sure the guests are happy and the hosts are behaving according to regulations. She also appears to act as a liaison between Westworld's Board of Directors and Ford.
Elsie Hughes is a Behavior Specialist working under Bernard Lowe.
Elsie helps with coding, debugging, and processing the hosts as they receive updates.
Ashley Stubbs is the Head of Security for Westworld.
Stubbs has a healthy level of skepticism when it comes to the hosts following their programming, and tends to take on potentially risky retrieval missions himself.
Lee Sizemore is the Head of Narrative at the parks.
Most of the storylines and dialogue you see the hosts act out in the park are all Sizemore's design. Based on recent events, however, it appears that Ford has the power to nix any of Sizemore's narratives and implement his own.
Felix Lutz is one of the Livestock Management employees.
It's Felix's job to patch up the hosts after they've been shot, stabbed, or otherwise incapacitated. But Felix "borrowed" a coding console from behavior and has been experimenting with doing his own programming on the side.
Sylvester is Felix's partner in the Livestock Manufacturing lab.
He has no patience for Felix's experiment with coding, and seems resolved to his role as a "butcher."
Maeve Millay is one of the hosts (robots) in Westworld.
Maeve is currently the madam of the Marisposa — a saloon/brothel in Sweetwater. Maeve frequently lands on Felix and Sylvester's operating table.
Clementine Pennyfeather is one of the host prostitutes working at the Mariposa under Maeve.
She specializes in finding newcomers and welcoming them to Westworld.
Dolores Abernathy is the oldest host still in Westworld.
Since she's the oldest park host, Dolores could have been manufactured up to 30 years ago. Stubbs says that she's been updated so many times "she's practically brand new." Dolores seems to be breaking out of her typical programming, though the cause is a mystery.
Teddy Flood is another host with a troubled past and a penchant for gunslinging.
He often accompanies guests on bounty hunts, or tags along with his programmed love — Dolores.
The Man in Black is a (so far) unnamed human character who has been coming to Westworld for 30 years.
The Man in Black has essentially been visiting the park since it opened. He's an expert player of the game, and gets special park privileges due to his mysterious V.I.P. status. We're pretty sure he runs a medical foundation of some kind out in the real world.
Lawrence/El Lazo is a host who spent most of season one with the Man in Black.
He's referred to by other hosts as a very dangerous man, likely due to his criminal group run under the name El Lazo.
Logan is a Westworld guest who has been to the park enough times before that he's familiar with many of the storylines and characters.
While in Westworld he's more of a sexual deviant and murderous kind of guy. This trip he brought along his coworker (and soon-to-be brother-in-law) William.
William is visiting Westworld for the first time.
Unlike his friend, William's more of a "white hat" kind of good guy who is predisposed to treating the hosts like humans. Back home, he works under Logan as the Executive Vice President at an unknown company.