From his accent, James Delos was born in Scotland and was known to have been a "self-made" man by founding the company of Delos. He also had at least two children: Logan and Juliet. His children are American.
Was mentioned by William.
James Delos is first seen visiting Sweetwater early in the the park's history. With the Hosts, including Dolores Abernathy and Teddy Flood frozen around them, James and William have a conversation about the potential of the park. William tells him that if James can't see the potential for data-mining of the guests, then he is not as good a businessman as he has heard. James likes William's courage at challenging him, and invites him to tell him what kind of ideas he has in mind.
Later, James is at his retirement party, having seemingly passed over Logan for control of the company in favor of William. James mentions that he does not have much time left and coughs repeatedly, indicating that he is ill.
We see James in a stylish apartment, and he is notified he has a guest. It turns out to be William, and James asks when he will be able to get out of his confinement. William tells him that they are monitoring him, and need to do some tests on him to determine if he can be released. This scene repeats several times, including when William is the age of the Man in Black, and we find out that James is a host in whom they have implanted the memories of James as a test. Host James appears to be lasting a number of days working fine, but eventually he he breaks down and the Westworld staff have to burn down the apartment and start over again.
Eventually, William comes to the realization that trying to keep Delos immortal was a mistake, and leaves an unstable malfunctioning Delos to wreak havoc on his apartment, telling the technician to avoid incinerating him and keep him under observation for a few days.
Bernard and Elsie find a locked room in a secret lab in Sector 12, where host James is barely functioning after having been left alone for so long, having destroyed the most of the room and killed the technician. After a scuffle Bernard manages to incapacitate host James, and Elsie incinerates him to put him out of his misery. They realize that Delos wants to sneak James's downloaded mind out of the park through Peter Abernathy.