Why there is no Interstate 50

The Interstate highway system is one of the great public works of all time. I have had a long fascination with the system, what it has done for America, and the places it has taken me and my family. I figured out years ago that the numbering system has even-numbered routes ending in zeros (such as I-10, I-20, I-80, I-90) running east and west across the country and odd-numbered routes ending in fives (such as I-5, I-15, I-25, I-95) runing north and south. Other even- and odd-numbered routes, oriented basically east-west and north-south respectively, fill in the rest of the system.

So one day, several years ago, I was studying a highway map of the United States and was surprised to find no Interstate 50 anywhere in the country.

"Why is there no Interstate 50?" I asked one of my daughters who was sitting nearby. The question was genuine.

I did not yet know, but found out from subsequent research, that when the new system was imposed on the country, overlaying the old U.S. highway numbering system, it was decided that duplicate numbers from the two highway systems could not co-exist in the same state.

The east-west even numbers of the old U.S. highway system increase from north to south (U.S. 30 is farther north than U.S. 50, for example). The east-west even numbers of the new Interstate system decrease from north to south (I-80 is farther north than I-10). The duplication would have become a problem in the middle latitudes of the country, where 50s and 60s could likely run through the same middle states. So, the people who think up these things merely decided never to construct an I-50 or an I-60.

And that is why there is no Interstate 50. Or 60.