building of the Mackinac bridge, completed in June 1958

Oldsmobile provided a fleet of convertibles so that beauty queens from all over Michigan could participate.

Why such a big deal? Well, it's the only bridge from one half of the state across Lake Michigan to the other half of the state, and in the years just before the Mighty Mac was completed, car ferries provided regular passage over the Straits of Mackinac, says Lowell Thomas, “with only minor inconveniences, such as waiting in line for 19 hours.”

from a big gallery the Keyhole Bar and Grill posted on their facebook page

https://www.facebook.com/pg/goodtimesgoodfood/photos/?tab=album&album_id=351730298179308

https://www.mackinacbridge.org/fares-traffic/fare-schedule/#passenger

and you can find some other interesting old movies made for schools at https://www.youtube.com/user/USAutoIndustry/videos

https://www.hemmings.com/blog/2015/07/29/midweek-matinee-the-five-mile-dream-1958/
https://blogs.lib.msu.edu/red-tape/2018/jun/june-25-1958-first-governors-walk-across-mackinac-bridge/
http://www.mightymac.org/58mackinacbridgeparade2.htm