Spearfish to Fort Thompson is 257.7 miles and takes about 4h 20m via I 90 and SD 47, with a fuel budget near $40 and enough daylight to finish in a day. This drive stays entirely within the Great Plains region, offering a straightforward journey across South Dakota. You'll primarily be on interstate highway, making it a practical choice for getting from point A to point B efficiently. Consider this route if you're looking for a direct path with minimal detours, suitable for a single-day trip.
Trip Pace
Same-day drive is realistic
A same-day return is possible, but it will make for a full day on the road.
Break Rhythm
1 planned break
Plan on a short reset every 3 to 4 hours to stay fresh behind the wheel.
Midpoint
128.9 miles from Spearfish, SD
A natural place for your longest stop of the day
, about 2h 7m into the drive
.
Main Roads
Road
Distance
Duration
I 90
236.2 mi
3h 46m
SD 47
19.4 mi
28m
SD 248
0.8 mi
1m
East Jackson Boulevard
0.5 mi
1m
North Main Street
<0.1 mi
<1m
BIA Route 4
<0.1 mi
<1m
Longest stretch:
I 90
— 236.2 mi, about 3h 46m
Traffic on I-90
Hour-of-day weekday pattern from 34 FHWA count stations on your route.
Peak
4 PM
~757 veh/hr typical
· worst 1,042
Quietest
2 AM
~28 veh/hr
Peak-to-quiet ratio
27×
busier at peak than in the quiet hours
12a6anoon6p11p
Averaged across 52 weeks of 2023 FHWA Travel Monitoring Analysis System data. Weekday hours only (Mon–Fri).
Turn-by-Turn Driving Directions
Step-by-step road directions between Spearfish, SD and Fort Thompson, SD.
1
Start on I 90 Business
85 ft·30 sec·North Main Street
2
Continue on I 90 Business
166 ft·9 sec·North Main Street
3
Turn right onto East Jackson Boulevard
0.5 mi·1 min·East Jackson Boulevard
4
Take the ramp
0.3 mi·37 sec
Toward I 90 East, US 85 South
5
Merge onto I 90; US 14; US 85
14 mi·14 min·I 90; US 14; US 85
6
Continue on I 90; US 14; SD 34
7.6 mi·7 min·I 90; US 14; SD 34
7
Continue on I 90; US 14; SD 79
24 mi·24 min·I 90; US 14; SD 79
8
Continue on I 90; US 14; US 16 Truck; SD 79
191 mi·3 hr 1 min·I 90; US 14; US 16 Truck; SD 79
9
Take the exit
0.3 mi·50 sec
10
Turn left onto SD 248
0.8 mi·1 min·SD 248
11
Continue on SD 47
19 mi·28 min·SD 47
12
Turn sharp right onto BIA 4
65 ft·1 sec·BIA Route 4
13
Arrive at destination
BIA 4
Trip Plan
Given the 4h 20m duration, you can comfortably complete this trip in one day. Aim to depart in the morning to allow for any unforeseen delays and to maximize daylight. With only one recommended stop, plan your fuel and rest breaks strategically, perhaps around the halfway point. The longest stretch without a significant change in road is over 236 miles on I 90, so ensure you have enough fuel before embarking on that segment to avoid any last-minute searches for a gas station.
Morning Departure
An early start around 7-8 AM gets you there with plenty of daylight left.
Evening Departure
A late afternoon start means arriving after dark. Morning is better.
You can normally do this drive in one day.
Plan roughly 1 meaningful break for fuel, food, and rest.
The halfway point lands around 128.9 miles from Spearfish, SD, or about 2h 7m into the drive.
The longest continuous stretch on this route runs about 236.2 miles.
This is a comfortable same-day trip.
Departure
Before you leave
Start with fuel, water, and navigation already sorted so the first hour feels easy.
First stop
Around 57 miles or 58m in
Use this first pause for coffee, a restroom break, and a quick traffic check ahead.
Halfway reset
Around 128.9 miles or 2h 7m in
This is the best place for your longest stop, a real meal, and a full fuel check.
Final approach
Final hour starts around 3h 25m
Traffic, exits, and arrival timing usually matter more near Fort Thompson, SD than in the middle of the route.
Before You Leave
+
Open the route before leaving Spearfish, SD so your first major turns are already loaded.
+
Leave with enough water and a charging cable within reach, not packed away.
+
Check your fuel range against the first long segment, especially if you are starting outside city service areas.
Day 1
Settle into the route from Spearfish, SD
This is one driving day of about 257.7 miles and 4h 20m.
Your first comfortable stop window is around 57 miles from Spearfish, SD.
This route can stay practical as a one-day drive if traffic stays reasonable.
Plan about 1 real break rather than only quick fuel stops.
The longest stretch is on I 90 for about 236.2 miles.
Where to Stop
Rest stops, refuel points, and overnight suggestions along this route.
Place data sourced from public business listings. Hours and availability may vary.
Heads-up: tricky spots
5 of 7
5 decision points cluster between mile 0 and 257.7 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.
3
0 mi into trip|~0m in|I 90 Business / North Main Street
Continue onto I 90 Business / North Main Street
Navigation decision point
4
0 mi into trip|~0m in|East Jackson Boulevard
Turn right onto East Jackson Boulevard
Navigation decision point
5
0.6 mi into trip|~2m in
Take the ramp toward I 90 East, US 85 South
Multiple destination signs - pick the right one
Toward I 90 East, US 85 South
4
237.4 mi into trip|~3h 50m in|SD 248
Turn left onto SD 248
Navigation decision point
5
257.7 mi into trip|~4h 20m in|BIA 4 / BIA Route 4
Turn sharp right onto BIA 4 / BIA Route 4
Sharp turn - reduce speed on approach
Fuel & Cost
Regular Gas
$42.85 one way
$85.69 round trip
$4.22/gal25.4 MPG avg90 kg CO2
Fuel Type
$/gal
One Way
Round Trip
midgrade
$4.60
$46.67
$93.34
premium
$5.18
$52.59
$105.17
diesel
$5.35
$54.28
$108.56
No toll roads detected on this route.
Estimated Trip Cost (one way, 1 person)
Fuel
$43
Meals
$25–$50
Total
$68–$93
Rough estimate based on US averages. Hotel $80–$140/night, meals $25–$50/day.
Estimated CO2 emission: 90.2 kg one way.
Prices: EIA weekly data, 2026-06-01.
Driving Electric?
About $27 in charging
· 0 stops
· 67% less CO2
Vehicle Type
kWh
Stops
DC Fast
Home Charge
Average EV
77.3
0
$27.06
$12.37
Efficient EV
64.4
0
$22.55
$10.31
EV Truck/SUV
103.1
1
$36.08
$16.49
Gas CO2
90 kg
EV CO2
30 kg (67% less)
Plan for 0 charging stops, roughly every 270 miles. Allow 25-40 minutes per stop at a DC fast charger.
DC fast charging avg $0.35/kWh. Home charging avg $0.16/kWh. US grid CO2: 0.39 kg/kWh.
Travel Intel
Current conditions at both ends of the drive.
Forecast as of Jun 2, 2026
Origin
Spearfish, SD
Afternoon
in Spearfish on Wednesday
Local time
1:08 PM
MDT
Current temp
76°F
Showers And Thunderstorms Likely
E 7 mph65% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued June 2 at 2:37PM MDT until June 2 at 3:45PM MDT by NWS Rapid City SD
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued June 2 at 2:34PM MDT until June 2 at 3:00PM MDT by NWS Rapid City SD
Destination
Fort Thompson, SD
Afternoon
in Fort Thompson on Wednesday
Local time
2:08 PM
CDT
Current temp
88°F
Sunny
SSE 18 mph11% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued June 2 at 2:37PM MDT until June 2 at 3:45PM MDT by NWS Rapid City SD
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued June 2 at 2:34PM MDT until June 2 at 3:00PM MDT by NWS Rapid City SD
Seasonal Notes
Summer travel usually means heavier construction, hotter rest stops, and busier weekend traffic around major cities.
Winter travel shortens daylight, so a route that looks manageable on paper can feel much longer after dark.
Holiday weekends tend to make both departure and arrival windows slower than the raw route time suggests.
Time zone
1 hour later
The destination clock does not match departure time, so double-check hotel check-in windows and late arrival plans.
Temperature spread
12 degrees warmer at arrival
A meaningful temperature swing is a good cue to rethink layers, water, and how soon you want to arrive.
Road read
4h 20m on the road
An early start around 7-8 AM gets you there with plenty of daylight left.
Weather data from the National Weather Service. Conditions may change; check closer to your travel date.
National Parks Near This Route
Worth a detour if your schedule allows.
Mount Rushmore National Memorial
National Memorial
Majestic figures of George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln, surrounded by the beauty of the Black Hills of South Dakota, tell the story of the birth, growth, devel...
18 mi from route
~46 min detour
Free
near mile 44.4
The rugged beauty of the Badlands draws visitors from around the world. These striking geologic deposits contain one of the world’s richest fossil beds. Ancient horses and rhinos once roamed here. The...
24 mi from route
~60 min detour
$30
near mile 106.6
Park data from the National Park Service API. Alerts update every 2 hours.
More Details
What kind of drive is this?
This is a highway-focused drive, with 100% of the journey taking place on major roads. You'll experience a significant stretch of 236.2 miles on I 90, which means consistent speed limits and a predictable driving experience. The route transitions to SD 47 and SD 248, but these are also well-maintained highways. Expect a smooth, uninterrupted drive for the most part, ideal for covering ground quickly across the South Dakota landscape.
100% highway — fuel and pacing are the main things to plan.
13 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 236.2 mi on I 90.
How Hard Is This Drive?
3/10
This is a straightforward highway drive that stays mostly on I 90 and SD 47. There are only a few real navigation decisions along the way. The trickiest moment comes early in the drive near I 90 Business / North Main Street.
Driving Effort3/10
Easy - simple navigation with a manageable amount of wheel time
Balances navigation complexity with total wheel time.
This is a straightforward 4h 20m drive. You will face about 7 decision points, but nothing that requires special attention if you follow navigation.
Where does it get tricky?
The main spots that need attention: near the start (I 90 Business / North Main Street): Navigation decision point; near the start (East Jackson Boulevard): Navigation decision point; at 0.6 miles: Multiple destination signs - pick the right one.
Spearfish is in the Black Hills of South Dakota. Although Spearfish is a small community with 14,000 residents, it is the commercial and academic center for several towns in the Black Hills and nearby Wyoming and Montana, attracting more than a million visitors each year with its museums, festivals and natural beauty.
The longest stretch is about 236.2 miles on I 90. The full list of main roads is in the Roads section above.
Yes — we found about 18 rest areas or service plazas within a short detour of the route (from OpenStreetMap). See the Rest Stops tab under Nearby Places for locations and mile markers. Plan to stretch, use the bathroom, and top off fluids every 2–3 hours on longer drives.
Yes, with realistic expectations. Build in a stop roughly every 2 hours, have snacks and activities ready, and check the Nearby Places tabs for kid-friendly stops along the way.
Mostly yes along the main roads, but rural stretches through SD can have sparse or no coverage. Before you leave, download offline Google Maps or Apple Maps for the route, and consider downloading music or podcasts instead of streaming. If you depend on data for navigation, keep a paper backup of the turn-by-turn directions.
The main spots that need attention: near the start (I 90 Business / North Main Street): Navigation decision point; near the start (East Jackson Boulevard): Navigation decision point; at 0.6 miles: Multiple destination signs - pick the right one.
Yes — Mount Rushmore National Memorial and Badlands National Park. See the National Parks section for detour distances and tips on detours.
Possible but tiring. At 4.3 hours each way, an in-and-out day trip would put you behind the wheel for 8.7 hours — manageable with a long break at Fort Thompson, SD, but most travelers stay overnight.
