In Journal of a Novel: The East of Eden Letters, Steinbeck writes about naming this family: "I do not have the name yet. I think it might be Canable. No, that is a double or rather a triple meaning I don't want. The name is so important that I want to think about it. I remember a friend of my father's—a whaling master named Captain Trask. I have always loved the name. It meant great romance to me."

Cyrus Trask is, like Samuel Hamilton, the patriarch of his family. He leaves a pregnant wife behind when he is inducted in the Union Army in 1862 during the Civil War. On his return, soon after the birth of his first son later that year, he is missing a leg and has the clap. He "is something of a devil—had always been wild." He proceeds to rule his household with an iron hand, and wildly exaggerates his participation in the war, lying so persuasively that even he seems to believe his own fabrications. By mastering military matters, he becomes a prominent advisor in Washington, D.C. His bequest to his sons after his death amounts to more than $100,000. How he acquired that much money is a subject of speculation in the novel.