Today, thanks to my friends at FOX 17, I learned that a three and half mile stretch of US 131 is officially I-296. 

It's the stretch of between I-96 and the Ford Freeway (I-196). It was officially designated I-296 when it opened in 1962. It is one of the few roads that is assigned both U.S. Highway and Interstate status.

I-296 even has its own Wikipedia page!

“I’m not sure why they named it 296, because there are enough ‘96s’ in the area,” John Richard at the Grand Region office of the Michigan Department of Transportation told FOX 17 News. 

And he was right. Eventually the Michigan Department of Transportation thought the I-296 signs on US 131 were just confusing motorists, so they petitioned the federal government to remove the signs in 1979.

There were no signs saved for the curious, but I think there should be a 'I still call it I-296!' t-shirt, don't you?

According to FOX 17 News, you can still find the I-296 designation on some government maps like this one.