MileCheckSouth Dakota is an I-90 state: one long east–west corridor past the Badlands and the Black Hills, with a lot of open country in between. Here's how the mile markers work — including a quirk SDDOT is upfront about — and how to see your exact position plus live DOT alerts in real time.
How South Dakota numbers its highways
South Dakota's markers count up from the west and south edges of the state. On I-90 the numbers start at 0 at the Wyoming line and climb east to about 400 at Sioux Falls; I-29 starts at the Iowa line and rises north toward North Dakota. Here's the quirk: SDDOT calls its signs mileage reference markers, and says plainly that the numbers are reference points rather than exact odometer miles. In practice that means you should trust the sign as a location, not a tape measure — it still tells a trooper or a tow truck exactly where to find you. Mile marker data for every South Dakota highway is bundled into MileCheck and works offline.
The corridors people actually drive
- I-90 crosses roughly 413 miles from the Wyoming line past Rapid City, Wall, and Chamberlain to Sioux Falls.
- I-29 runs north–south along the eastern edge through Sioux Falls, Brookings, and Watertown.
- US-14 and US-16 serve the Black Hills country toward Mount Rushmore; US-83 and US-281 cross the middle of the state north–south.
Where mile markers matter most: the long middle
Between Rapid City and the Missouri River, exits get sparse and the towns small. If Wall Drug's billboards are counting down the miles for you, the mileposts are doing the same thing more precisely. A breakdown or a spun-out car between exits gets reported by mile marker — it's the reference dispatch, plows, and tow drivers all share.
Winter closures and prairie wind
Like its neighbor to the north, South Dakota closes interstates when blizzards or ice make travel unsafe, and those closures are announced by mile range. Winter systems can shut I-90 across whole counties, and spring flooding along I-29 in the Missouri and Big Sioux valleys has forced long detours too. Knowing the mileposts — and getting the alert before you're committed — is how you avoid sitting at a closure gate.
Live South Dakota DOT alerts, in one place
MileCheck pulls live road alerts from South Dakota's DOT: closures, crashes, construction, and winter conditions, tied to the mile marker and direction so you can see what's ahead of you on your route before the next long, empty stretch.
Everyday and emergency
Whether you're crossing to the Black Hills in January, reporting a breakdown east of Wall, or telling a friend which exit to meet you at, the mile marker is the location South Dakota's roads run on. MileCheck shows yours in real time, down to a tenth of a mile, even where the cell signal drops — with CarPlay and Android Auto for the long haul.
Keep reading
Nearby state guides: Iowa · Minnesota · Montana · Nebraska · North Dakota · Wyoming
South Dakota drawbridges: every movable bridge, its opening rules →
Essentials: What to tell 911 on the highway · How to find your mile marker · Browse the live mile marker map · All 50 states