This one looks like it was built before anyone noticed.
Leading the charge Already testing to open in a few days. Great location adjoining I90 just a couple miles East of Spearfish. BTW, 6 stalls. In addition to las nt distance travelers this site will really help for people wanting to tour the Northern Black Hills. Tesla already has a strong presence in Southern Hills -Custer due to the annual rally and Rapid City to the East.
The article says Exit 8, which is northwest of Spearfish, rather than the one at Exit 14 east of Spearfish.
Their Facebook page also explicitly says Exit 8:
Exit 14 and Exit 8 / Phillips 66.
The photo in the article matches with storage units shown on Google Maps StreetView where it says there's a SpeedyMart. StreetView doesn't show a gas station there, so it must be a relatively new build. It looks like the actual Supercharger location is closer to where Google Maps shows "I90 Self Storage" than SpeedyMart.
There's nothing else around that location. Perhaps they were asked about Exit 14 because there's other stuff around there, but negotiated for Exit 8 because they'd have a captive customer.
Supercharger: Spearfish, SD
Street Address: 3275 Old Belle Rd*
City: Spearfish
State: SD
Zip: 57783
Country: USA
Stalls: 6
GPS: 44.520607, -103.890924
* A Google search gave the address as Old Bell Rd, even though Maps indicates it's on McGuigan Rd and Old Belle Rd is north of I-90.
GasBuddy has the Exit 8 Philips 66 as 3275 Old Belle Rd, Interstate I90, Spearfish, SD 57783
However, I-90 Self Storage, to which it is very close has an address of 3020 McGuigan, Box 728, Spearfish, SD 57783.
EDIT:
Exit 8 Phillips 66 set to open Aug. 1 is from July 2016 saying it was opening August 1st 2016. The address is listed in that article as 3275 Old Belle Rd.
@BlueShift
On I-90/US-14 and close to US-85.
A good splitter of a 142 mile gap.
As the article says, expect Wall, SD which will split the 134 mile gap between Rapid City, SD and Murdo, SD.