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100 years of US routes: 1926-2026
Many people (myself included) have an odd fascination with the superlatives of just about any topic. As it relates to highways, a common question is "What is the longest US route?" (answer) And then related questions branch off from there:
Eventually the questions start swinging around to the opposite extreme, and those are the topics of this post. Specifically we set out to answer these questions:
What is the shortest US route?
What was the shortest US route historically?
What is the shortest 2-digit US route?
What was the shortest 2-digit US route historically?
But first, a caveat: this article only takes mainline US routes into consideration. There are lots of bannered US routes (e.g. Business US xx, or Spur US xx) that are very short (some even less than a mile). There are also suffixed US routes (e.g. US xxA, or US xxN) that are very short. But none of those are mainline US routes; rather they are all auxiliary US routes (i.e. their numbers are the same as the mainline route to which they connect). This article excludes bannered and suffixed US routes, and focuses only on mainline US routes.
The shortest US route, currently
In AASTHO's most recent route log (1989), two routes were listed at 42 miles each: US 266 and US 730. However, the mileages published by AASHTO were rounded to the nearest integer, and were subject to a non-trivial error margin. Using a more precise method of measuring, we find that US 266 is 43.1 miles in length, while US 730 is only 41.3 miles long. So currently US 730 is the shortest US highway.
The shortest US route, future
The difference between US 730 and US 266 is less than two miles. Washington State DOT has planned a change in the alignment of US 12, which will presumably create a need to extend the US 730 designation by at least three more miles in length. This WSDOT map illustrates their plan to extend US 730 northward along current US 12 to a junction with the new US 12. Assuming this project gets completed, one collateral result will likely be that US 266 becomes the shortest mainline US route:
The shortest US route, historically
This is quite a long story, but maybe you're just here for a quick answer, so I'll start with that: US 320 was the shortest mainline US route. It ran between Riverton and Shoshoni (WY) and was a mere 22.1 miles long.
Full disclosure: up through 2025, a different answer was posted on this page (and that answer had long been accepted in an online community of road enthusiasts). However, in 2026 I accidentally learned some additional information, which led to some questions, followed by more in-depth research, and now I am quite convinced that the old answer was incorrect. As far as I know at the time of writing, this new answer (US 320) runs counter to every other answer online, as well as (I'm sorry to admit) the first edition of my own book (which was published in 2025). So to back up my claim, a full explanation follows.
US 630 was not a signposted route
Among highway historians it is sometimes asserted that US 630 was the shortest-ever mainline US route. And that would have been true... if US 630 had been an actual route. It showed up on the Nov. 1926 map of official US routes approved by AASHO (now AASHTO), so it was definitely planned. If we measure its intended route, it would have been only 2.9 miles long. How does our modern measurement compare to the length of US 630 as listed on the early route logs? Well... turns out it never appeared on any route logs. By the time AASHO published their first US route log just a few months later (Apr. 1927), US 630 was already gone. Why? Because Idaho objected; they included that short segment as part of a longer auxiliary route that they signposted as US 30N (more details on this page). So US 630 was never signposted, and therefore it doesn't count as a "real" US route.
Well then, what was the shortest "real" US route? At first glance, it would seem the obvious way to find an answer would be to look at the mileages listed in AASHO's route logs. But as it turns out, AASHO logs were not completely reliable (we will see more than one example of that below).
US 430's truncation was not AASHO-approved
US 430 appeared in the three earliest route logs (1927, 1929, 1932), and in each case it was listed at either 36 or 37 miles. However, I am quite certain that was a mistake. The route log mileages were based on the assumption that US 430 ran between Crystal Lake and Aurora (IL), but every map I have seen indicates that its true south end was in Geneva. At the time, eastbound US 30 came into Geneva, then south to Aurora, then southeast to Joliet, so there was no reason for US 430 to be dual-signed with US 30 between Geneva and Aurora. So if we look at US 430's actual mileage from Geneva to Crystal Lake, Illinois official state highway maps indicated it was really only 26 miles long (2+10+5+5+4):
c. 1932, IL DOT
As a reality-check, I measured the distance myself, and came up with a distance of 26.3 miles. So that puts US 430 in the running for the shortest US route. And it gets even more interesting: in 1933, US 14 was extended east from Winona MN into Chicago. Its Illinois segment was routed along part of US 430 (the part between Crystal Lake and West Dundee). So the 1933 issue (and only that issue) of Illinois' official state highway map showed that US 430 had been truncated to West Dundee, which left its total length at only 17 miles (2+10+5):
c. 1933, IL DOT
My reality-check yielded a distance of 16.5 miles. However, AASHO never authorized that truncation, and at any rate the following year Illinois extended US 330 such that it subsumed the remainder of US 430. So can we say the unauthorized and very brief 17-mile iteration of US 430 was the shortest US route? I think it's debatable, but at least worth mentioning.
What did AASHO's route logs say?
Now, with all that in mind, let's take a look at the historically-shortest US routes, according to the mileages listed in AASHO's three earliest route logs (and I have included the corrected mileage for US 430 in this list):
US 530 (25, 24, 22)
US 430 (26, 26, 26)
US 320 (26, 27, 27)
US 730 (26, 27, 27)
US 650 (27, 27, 27)
US 154 (27, 27*, 30)
*The 1929 log actually said 21 miles, clearly a typo.
So based on that, one would conclude that US 530 was the shortest US route, and that is the answer that was posted on this page for years. But then in 2026, I was adding some information to the US 650 page, and I just happened to notice that Colorado's 1934 and '35 official state highway maps showed the distance of that route as only 23 miles (rather than 27). Note in the following image: the "15" and "6" between Buena Vista and Salida do not refer to mileages, but rather to state highway numbers. The mileage between those junctions was actually shown within the highway line, adjacent to the US 650 shield:
c. 1935, CO DOT
That caught my attention, because the state DOTs are considered the ultimate authority for data about their own highways, and if US 650 was truly only 23 miles long, then that could possibly make it even shorter than US 530. So I did a reality-check, which yielded 23.2 miles. My initial thought was that I had found a new shortest US route... but then I realized, to be thorough, I should check the state highway maps for all of the other routes on the list above.
What did the official state highway maps say?
US 530: the earliest Utah state highway maps said 24 miles, but changed to 25 miles starting with the 1930 issue (12+8+5; that change may have been related to a slight reroute necessitated by Echo Reservoir, which was constructed right around that timeframe). My own approximation came to 24.3 miles:
c. 1931, UT DOT
US 320: the earliest Wyoming state highway maps said 22 miles, but changed to 23 miles starting with the 1935 issue. My reality check yielded 22.1 miles. In the following image, the "22" inside a circle represented not a state highway designation, but rather the mileage between Riverton and Shoshoni:
c. 1933, WY DOT
US 730: the earliest Oregon state highway maps said 27 miles (11+10+6, and Washington maps agreed with the 6 mile segment in their state). My own measurement yielded 25.7 miles, although I'm not sure if that slight discrepancy is the result of a realignment that may have been necessitated by Lake Wallula (McNary Dam began construction in 1947 and opened in 1954):
c. 1937, OR DOT
US 154: Kansas state highway maps said 27 miles. My reality check yielded 25.7 miles:
c. 1933, KS DOT
US 159: Even though this route was not commissioned until 1935, we still need to consider it, because at that time it was only 24 miles in length (5+14+5, according to this Kansas state highway map), or 24.8 miles (according to my reality check):
c. 1936, KS DOT
So, a more accurate list of the shortest US routes is arranged as follows:
US 320 (22.1 miles)
US 650 (23.2 miles)
US 530 (24.3 miles)
US 159 (24.8 miles, 1935-1942)
US 730 (25.7 miles, 1926-1942)
US 154 (25.7 miles, 1926-1938)
US 430 (26.3 miles)
Surprisingly it turns out that US 320 was the shortest mainline US route ever (or at least the shortest legitimate US route). But for how many years was that true? And did any other US routes hold the title after US 320 but before US 730?
Timeline: the shortest mainline US routes
US 320 remained the shortest US route until 1939. After that, a couple other US routes claimed the dubious honor for varying lengths of time. Here is a full timeline:
In 1926, and for the next 13 years, US 320 was the shortest at 22.1 miles.
From 1933-1934, an unauthorized iteration of US 430 was only 16.5 miles long, causing a brief asterisk in US 320's reign.
By the time US 320 was decommissioned in 1939, US 650 and US 530 had also been deleted, so for the next four years, US 159 took over as the shortest route, at 24.8 miles.
US 730 remained at 25.7 miles until it was extended in 1942, but it did not become the shortest route during that timeframe, because US 159 was not extended until the same year (1942).
In 1942*, and for nearly the next four decades, US 154 became the shortest US route (even though by then it had been extended to 36 miles). This remained the case until US 154 was decommissioned in 1979.
In 1979, US 730 became the shortest at 41.3 miles, and that remains the case through the present.
At some point in the future, US 266 will likely become the shortest at 43.1 miles.
*US 177 was commissioned in 1928. The 1929 route log listed it at 28 miles, and the 1935 log had it at 30 miles. If those figures were correct, then US 177 would have been the shortest US route from 1942 (when US 159 and US 730 were extended) to 1964 (when US 177 was extended). However, the only way US 177 could have been that short is if it ended in Tonkawa. But neither route log mentions Tonkawa; both list the south terminus as Three Sands Jct. Furthermore, OKDoT maps from 1942-1964 clearly show US 177 extended south of Tonkawa, ending at Three Sands. So US 177 could not have been only 30 miles long. It actually would have been 40 miles long, and therefore would never have been the shortest US route.
What about the shortest two-digit US route?
So far this entire discussion has been about three-digit US routes. These were originally envisioned to be shorter "child" routes that branched off from longer "parent" routes. In other words, it is not all that surprising that some three-digit US routes are quite short. But since two-digit routes are presumed to be longer, which one is the shortest?
Currently, the 13th-shortest US highway is a two-digit route. US 46 measures a surprisingly short 75 miles in length, and it is entirely in one state (although there is an interesting explanation for that). Currently there are 20 US highways with lengths less than 100 miles, and two of those are two-digit routes. Currently there are 65 US highways of less than 300 miles, and 11 of those are two-digit routes.
What was the shortest two-digit US route historically?
In the 1927 route log, US 48 was the shortest two-digit route listed, at 67 miles...
...and already by 1929, US 48 had been truncated on both ends, such that it was then only 50 miles long:
That was the shortest-ever two-digit US route. But US 48 was decommissioned in 1931. So what was the shortest two-digit US route after that? In 1931, US 94 [Naples to Miami] became the shortest two-digit route at 110 miles. (Incidentally, the next two shortest at the time were also east-west intra-state routes in Florida: US 92 at 163 miles [Tampa to Daytona], and US 98 at 193 miles [Pensacola to Apalachicola]). US 94 held the title for only five years, until US 46 was commissioned in 1936. At that time US 46 became the shortest two-digit, and has remained so ever since.
Research and/or image credits: Dale Sanderson
Page originally created 2022;last updated Feb. 26, 2026.
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