Black Rock Station (N39 52 41.1 W113 16 17.5) (M) east

Location: NW1/4SE1/4 Section 12, Township 11 South, Range 12 West, Salt Lake Meridian, 13 ¾ miles from Dugway. 

Also known as Butte, or Desert Station, it was named for the black basalt outcropping just to the north of the road and the monument. Sharp says it was also known as Rock House. Initially called Butte or Desert Station, the rock structure was constructed as part of trail improvements undertaken by the Overland Mail Company after acquiring the Express in July 1861.

Little is known about Blackrock station, or its usage possibly due to it being a non-contract station. A structure of native black stone was apparently built here in 1861, while other structures in the area are suggested. Reconnaissance and infrared photographs have also failed to produce any evidence. Only a vandalized monument marks its general location.

Informants say the station site lies west and north of the volcanic outcrop known geographically as Blackrock. The old Lincoln Highway (1913-1927) first encountered and utilized the old Overland Route about ¼ mile east of the monument. This routing was used as an alternate to the main road during wet weather.  http://www.expeditionutah.com/featured-trails/pony-express-trail/utah-pony-express-stations/

BLACK ROCK STATION* 

Fike and Headley list this station thirteen and three-fourths miles from Dugway.  Several sources identify Black Rock or Blackrock as a station between Dugway and Fish Springs, although Fike and Headley add Butte and Desert Station as alternative names. The exact location of the station, originally known as Butte or Desert, remains unknown. The Overland Mail Company may have erected a stone structure near the Blackrock volcanic formation after July 1861, but its connection with the Pony Express is uncertain because it did not appear on the 1861 mail contract. A damaged monument marks the general area of the station site.

http://www.nps.gov/parkhistory/online_books/poex/hrs/hrs7a.htm#117