This is an image of a rock arch which spans an inlet of Lake Michigan on Mackinac Island, roughly between the Lower and Upper Peninsulas of Michigan.
The caption states:
ARCH ROCK
This natural rock formation, with a span of 50 feet, stands 149 feet above the blue waters of the Straits of Mackinac. There’s a beautiful view from the railing alongside, and this is one of the most photographed spots on the island. This scene is included on the Carriage Tours.
— Carriage tours are provided on Mackinac Island because no motorcars are allowed to land at the island, keeping the island in a state reminiscent of its history.
This card likely dates from the 1950s.