I called R.'s mother and stepfather and got stepfather D. I quizzed him about his first wife's cycling, and got the following. They married shortly after graduating college and they both got jobs almost immediately that were widely separated and thus had to have two cars. She had not had a car prior to their marriage. (This would be around '59 or '60.). His then-wife did have a bicycle, ridden occasionally for recreation and exercise. When they lived in NJ, she worked a couple miles from home and sometimes commuted by bicycle. He recalls virtually every one of their kids (between R. and I in age) having mothers who had bicycles; he saw those mothers riding those bicycles with their kids (destinations unknown) or by themselves, when he was out jogging.
So we now have NJ, MA and WA evidence of 1960s and 1970s cycling suburban housewives being a common and unremarkable sight.