There are many things in modern life that we used to think unthinkable. And another of them went away Sunday when a bomb threat forced the closing of the Mackinac Bridge.

The Mackinac Bridge authority sent out the above tweet Sunday afternoon to inform the public of what was going on. During this period all Bridge related public communication was shut down temporarily. This included the Mackinaw Bridge Authority's live news stream. Helicopter tours were temporarily suspended, too. And even the United States Coast Guard was involved, shutting down and securing the perimeter of the bridge.

Aside from the cost of an operation like this, for what, fortunately, turned out to be a hoax, it does point out the vulnerabilities of any public edifice, essentially putting it into the category of a "sitting duck". But in this case, it is the only, Michigan only, land link between Michigan's two peninsulas. While the population total of the Upper Peninsula isn't that large, still the headaches involved would be enormous. Business and shipping traffic could be re-routed around through Wisconsin, but the effect on a tourist town like St. Ignace would be devastating, especially on top of the recent economic downturns the area has endured over the past dozen or so years.

The Mackinac Bridge was talked about for many years, (in fact, back in the late 1800s there were discussions of a bridge spanning the Straits of Mackinaw, but finally, construction began in the 1950s and the Bridge opened in 1957.

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