Mary Motschenbacher, 68, a medical transcriptionist from Fargo, N.D., and her sister, Beth Boatz, a 67-year-old retired banker from Blaine, Minn., on their 1948 Plymouth, as told to A.J. Baime.

Ms. Motschenbacher: In 1947, our uncle, Laurence Boatz, bought this Plymouth new from the Corwin Chrysler dealership in Fargo, which still exists. In the mid-1960s, our dad took ownership. We had a good family, but we did not have a lot of material things, so this was a big deal.