What’s the Longest Highway in Illinois? Two Answers

I have done a road trip across Illinois both north/south and east/west and I can tell you that you better enjoy seeing corn if that's an adventure you decide to tackle. What is the longest highway in the Land of Lincoln? The truth is complicated and is two different answers depending on how you ask it.

What is the longest highway in Illinois and why is it complicated?

How you measure the longest roadway in Illinois depends on if you're asking about interstate highways or numbered highways. The longest interstate highway in Illinois is I-57 which traverses around 358–359 miles across the state.

The longest numbered highway across Illinois is by far the roadway that covers the biggest distance which is Highway 45. It's a 429 mile trek from the Kentucky border to Wisconsin or the other way around if you're traveling from the north to the south. Wikipedia says it's 428.99 miles, but I'm rounding it up.

Highway 45 has some interesting history. From what I can find, it appears that this Illinois highway was officially designated in 1926, but the paving started as early as 1914 and 1915. It was a part of the original American highway system in 1926. In total, it spans America from Michigan to Alabama. It's truly a Great Lakes to the Gulf adventure.

If you drive Highway 45, be very careful

Highway 45 has an interesting history that takes you literally through the middle of America, but it's also considered one of the most dangerous roads in the country.