This image shows a few of the cars transported across the Straits of Mackinac by a ship of the same name before the construction of the bridge connecting Michigan with Canada.
The description states:
ABOARD “THE STRAITS OF MACKINAC”
One of the earliest State Ferries operating between St. Ignace and Mackinaw City, still in operation.. S 68
–The ship shown here was built in 1928 and may have continued until the 1950s, when ferry service was discontinued. This image likely dates from the 1950s based on the car models visible.