Indiana State Road Numbers

As someone that spends a LOT of time looking at maps, I notice that most states have no rhyme nor reason to the numbering of their state roads. Most states number them in the order they were created, or legislated. Indiana is, now, not one of those.

In the beginning, 100 years ago this year, Indiana started creating a State Market Highway system. At that time, there were only five state roads. OSR 1 ran, basically, down the center of Indiana north to south. OSR 2 was the Lincoln Highway. OSR 3 was the National Road (more or less). OSR 4 ran from JCT OSR 5 near Shoals to Lawrenceburg. OSR 5 connected Vincennes to New Albany.

Around 1924, talk was started about creating a “national” road system to take the confusion out of traveling in the age of Auto Trails and the myriad of names and directions. The system was ironed out over the next two years, coming to fruition on 01 Oct 1926.

And that is the day that Indiana did a wholesale slaughter of the state road numbering system.

Indiana decided to do the same thing with the numbering of state roads that the “national” system did: odd numbers travel north/south being numbered east to west, even numbers travel east/west being numbered north to south. For the most part, anyway.

There were exceptions. There always are exceptions. Yet, through some freak of numbering, the new United States highways, for the most part, just plugged right into the system. For example, US 31, US 36, US 40, and US 50 fit right into the Indiana system perfectly.

But the system was simplified, as well. In addition to the directions of the roads, and where the numbering started, Indiana also added the “mother/daughter” system. Main state roads were give one and two digit numbers, with three digit numbers being daughter routes to those. There were/are only two exceptions to the three digit daughter rule, but I will get to that later.

One of the purposes of the “daughter” system was to create a way to insert state roads into the system without totally destroying the order of the system.

The one major exception to the whole system was SR 67. There were discussions about US 67 connecting to Cleveland, OH, across Indiana. The plan was to number it SR 67, and change it if and when the time came. It never did. US 67 ended up traveling, more or less, due north through west central Illinois.

The Indiana numbering system works well. If you know the history. If you look at a map today, there are several things that stand out like a sore thumb. And those are really due to the United States highways that came to Indiana after 1926.

Let’s get back to the two three digit exceptions to the daughter rule. First, and most obvious to map readers, is SR 135. Yes, it is a major state road. No, it is not a daughter route to US 35. It used to be SR 35, until US 35 came to Indiana.

The other exception was SR 100. Ask anyone who knows, and SR 100 was to be a loop around Indianapolis. Unfortunately, the history of the road isn’t that simple. While SR 100 legally lasted (at least from I-465 to US 4) until 1 Jul 1999, it was replaced long before that by the same I-465. As a matter of fact, most of the contracts for the building of I-465 were actually issued as SR 100 contracts.

Now, to daughter routes. Marion County has a daughter route that connects to the Women’s Prison (used to be the Indiana Girl’s School) on, guess what, Girls School Road. It is SR 134. Yet, there is no SR 34 in Indiana. There was. There isn’t now. SR 34 became US 136 in 1951. There also used to be a LOT more daughters of SR 34: SR 234 (through Carmel – not the two that still exist), SR 334 (Zionsville – decommissioned just a few years ago), SR 434 and SR 534 (the original designation of the major part of SR 100 – the part that most locals know).

In southeastern Indiana, there are two daughters of SR 29: SR 129 and SR 229. These exist because before 1951, US 421 was SR 29 from Madison to just south of Boyleston.

I am sure that there are more examples of such numbering inconsistencies. SR 21 mostly became US 35. US 231 used to be part of SR 43 and part of SR 45, among others. Even in northwestern Indiana, there are a lot of x27s that are orphaned because US 27 was replaced by I-69 north of Fort Wayne.

But two roads that I am asked about quite often are SR 38 and SR 47. Strangely, SR 47 ends at SR 38 at Sheridan.

Although SR 47 spends most of the way traveling east and west, it is labeled north and south. As you travel east toward Sheridan, you are on North 47. I have never been able to find a reason for this. Nothing. INDOT has decommissioned part of this route from JCT SR 38 to JCT US 31.

SR 38 is a different story. It DID follow the pattern when it was created. The original SR 38 connected New Castle to Richmond. (Although US 36 didn’t exist east of Indianapolis, this location of SR 38 is between 36 and 40.) The State Highway Commission would eventually add to SR 38, displacing most of the route when it comes to numbering. It would follow the old “Crawfordsville State Road” from New Castle to Noblesville (with the rest of this Crawfordsville Road becoming part of SR 32), and, roughly, the Lafayette Road (Lafayette-Noblesville State Road) for the rest of its journey across Indiana.

So, although there are exceptions, there is some method to the madness of Indiana state road numbering. And, with a little thought and knowledge, it does make Indiana a little easier to navigate.

2 thoughts on “Indiana State Road Numbers

  1. I’ve never understood how SR 234 and SR 334 got their numbers when they were nowhere near SR 34/US 136.

    I remember reading somewhere a long time ago that SR 47 started as the US 41-Crawfordsville leg, which could have been considered either north-south or east-west given its route, and the state went with north-south. It was only when the road was later extended to US 31 that the north-south designation became retrospectively stupid. Wish I could find that source now. Might have been the old Highway Explorer site, which I miss.


    1. Hmmm….I thought I responded to this. I’m sorry.

      I think that somewhere along the line, 34 was decided to be a “placeholder” number for the Indianapolis area. I have been running it through my logic processors, trying to come up with a logical reason for it. The only answer I could come up with is “well, it’s CLOSE to Indianapolis.” Not a really good answer. The only other thing I can think of is that old 34 was the lowest east-west state road number available to use and ran into Marion County. Again, not a really good answer.

      Maybe the ISHC just got really lazy. Who knows?

      Liked by 1 person

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