The ‘Secret’ Code Behind Why 61 and 172 Are Numbered How They Are

It's one of those aspects of life that you see practically every day, but don't take the time to ask the question "why?". It's the rhyme and reason behind why our highways have the numbers they do including Highway 61, 172, 70, etc.

Get our free mobile app

I saw this interesting topic trending on Digg. It was referred to as the "secret code that the interstate highway signs in the US are telling drivers". Ooh...the suspense. The fact is it really isn't that much of a secret, but it is an interesting backstory about how our highways ended up with the numbers they did.

Here's the short version of what the video explained. The horizontal interstates that cross the country end in "0". The farther north the interstate, the higher the first number is which is why the interstate going through the middle of the country is our I-70. When you venture up into the land of the Children of the Corn (aka Iowa), you deal with I-80.

The vertical interstates end in 5, but what about Highway 61? It's obviously a major highway which stretches over 1,400 miles from Minnesota through Louisiana, so why doesn't it have a 5 at the end? (*face palm*) Mysteries do remain.

172 is a spur route which is why it has 3 digits and has numbers based off of the interstate it's associated with and eventually becomes 336. Following me?

The concept of the highway/interstate numbering system was for drivers to be able to navigate even without a map using the number sequences to help them understand approximately where they were.

The result? I'm not certain where this leaves us. (*face palm again*)