Missouri operates one of the largest state highway systems in the United States. The state highway system is distinctive because it is composed of both numbered state highways and a system of supplemental roads, designated by letters.
Missouri's Numbered Highways
Missouri's numbered highways, as shown in this site's unofficial route log, can be loosely categorized by number:
1-100
Many of these highways serve principal cities and towns in
Missouri. Only one highway without a US or Interstate
route designation, Missouri 5, shown at left with
Missouri 6 south of Milan, actually extends from one
border to another.
Some of these highways have offshoot highways that are numbered to match the "parent" road. Such derivative highways more commonly accompany US or Interstate routes, but there are some for state routes, too. Most derivative highways connect with their "parent" routes.
101-190
Many of these highways could be considered the back roads of
Missouri. Some of them are spurs or loops into state parks. A few
others are derivatives of two-digit federal or Missouri routes,
such as Missouri 163, pictured here at its southern endpoint
as it intersects with US 63 south of Columbia.
The route log denotes highways that serve as spurs or loops into state parks. It also shows derivative highways and their "parent" roads.
200 and above
Almost all these highways are derivatives of two-digit US or
Missouri routes, such as Missouri 254, pictured in a sign assembly
at its northeast endpoint in Hermitage.
However, Missouri is somewhat flexible in this regard, and some highways can be found in this range that do not have "parent" roads.
Missouri does not assign numbers in the 600, 800, or 900 ranges. Only one number is assigned in the 500 range, 571 (derivative of US 71). In the 400 range, a new number, 413, was assigned to a former section of Missouri 13 in Springfield in 2000. An additional number was assigned in the 400 range when the first phase of Missouri route 465 opened near Branson in 2003. All but one active number in the 700 range is a derivative highway.
Missouri Repeats Itself More Often Than Before
Missouri did not normally duplicate state numbers with any federal numbers (US route or Interstate highway) in the state. With the advent of the Interstate highway system in 1959, multiple state routes were renumbered. But the number of exceptions has grown in recent years. One longstanding exception was 59, a US route in the northwest part of the state and a Missouri state route in the southwestern corner. Then came Interstate 64 in the St. Louis area. Missouri 64 in west-central Missouri retained its number.
With the opening of the new Mark Twain Bridge in Hannibal in September
2000, Interstate 72 was extended into Missouri.
A short section of Interstate 72 is in Hannibal, while
Missouri 72 extends from Rolla to Jackson in SE Missouri. The
section of Missouri 72 from Ironton to Fredericktown has been
renumbered once before: it was originally Missouri 70. It was
renumbered with the advent of Interstate 70.
The designation of the Chicago-Kansas City Corridor along Interstate 35 and US 36 as Missouri 110 created yet another duplication, with Missouri 110 in Jefferson County. MoDOT explained to me that it does not consider this to be a true duplication, and there was also the desire to avoid inconveniencing Jefferson County residents, by avoiding changing addresses along the route.
Another exception is 49. It's been a state route number in southeastern Missouri since 1926, at least. On December 12, 2012, the route number 49 also appeared on the newly designated Interstate 49, the US 71 freeway in west-central and southwestern Missouri. Interstate 49's northern endpoint is at Interstates 435 and 470 in Kansas City; its southern endpoint will eventually be at the Arkansas state line, but it currently ends about 10 miles north of the line near Pineville.
Most odd-numbered Missouri highways run north-south while most even-numbered Missouri highways run west to east. This is more of a general principle than a hard-and-fast rule, however. In addition, Missouri 148 and Missouri 202 in the northern part of the state have, since 1968, been numbered to match their corresponding routes in Iowa even though they are north-south highways.
There are a few spur routes from state roads, and Missouri 64 also has two derivative highways with letter suffixes, 64A and 64B. These are the only Missouri highways with letter suffixes.
Missouri's Supplemental Roads
The supplemental roads are designated by letters on a county-by-county
basis, but they are not county highways. They are owned and
maintained by the Missouri Department of Transportation, just as
the numbered state highways are.
The sign assembly on the left shows a junction of both types of highways. Missouri's numbered state highways are indicated with signs using the state's outline, while supplemental highways are designated with letters in a square outline. This intersection in the Montgomery County town of Wellsville runs the gamut from AA to ZZ as those roads intersect Missouri 19.
This site doesn't attempt to cover the supplemental roads. They often serve the same role that farm-to-market roads serve in Texas. Supplemental roads beginning with R are used for roads to conservation or park facilities. (In Missouri, the conservation and parks departments are separate.)
Disclaimer: This is an unofficial site. Route logs and other information have been the result of research through official state maps and other publications, as well as personal observation. The Missouri Department of Transportation has its own site. All photographs at this web site were taken by me, copyright 1998-2015, Mark Roberts, all rights reserved, unless otherwise noted.
Mark RobertsOakland, California
E-mail: Please see the Contact Information page.