Dear Ms. Kreiser,
Thank you for posting your request on History Hub!
The Mackinac Bridge opened to traffic on November 1, 1957, while there are some photographs of the 1958 dedication online, photographs of various U.S. Army activities dating from 1940 to 2007 are in the custody of the National Archives at College Park - Still Picture (RDSS). Please contact RDSS via email at firstname.lastname@example.org and their web site is https://www.archives.gov/dc-metro/college-park/photographs-dc.html.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDSS. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck with your family research!