Everybody Thought We Were Crazy: Dennis Hopper, Brooke Hayward, and 1960s Los Angeles by Mark Rozzo:
His parents were essentially Dodge City townies. Marjorie Mae Davis was a teenage swimming phenom; she was known in the family lore as being a state backstroke champion who had aspirations to compete in the 1936 Summer Olympic Games in Berlin. In photographs, Marjoie is lithe and athletic, with apple cheeks, vivid eyes, and a broad smile. Dennis’s father, Jay Millard Hopper, worked at a grocery store, Busley Brothers IGA, and eventually rose to manager. A picture of the young Jay shows him with upswept hair and a full beard, standing beside a Coca-Cola delivery truck and wearing a clerk’s apron. He made this workaday outfit dashing with an Art Deco-patterned shirt, a neckerchief, and a proud grin. (Jay’s father had been a grocery store clerk as well, eventually making a living as a meter reader for the Kansas Power Company.) Marjorie and Jay were good-looking kids, and they got married in a hurry, on August 21, 1935.
Their son, Dennis Lee, was born almost exactly nine months later at St. Anthony’s Hospital in Dodge City on May 17, 1936. Marjorie and Jay named him after Dr. Foster Leonard Dennis, the hospital’s chief of staff. His middle name came down from Majorie’s maternal grandmother, Lee Masters McInteer, known as “Mammy Mack”—intense, eccentric, funny, given to strange habits. She practically lived off Sucrets throat lozenges and liked to carry a shillelagh, whacking people if they crossed her. Jay liked to tease Marjorie that she took after Mammy Mack. He was nineteen years old and Marjorie eighteen. Marjorie would say of their young family, “We all grew up together.”