The Blackhawk plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
Partly cloudy
Sunny; warmer
Mostly sunny
Partly cloudy
Partly cloudy; cooler
Mostly cloudy
Chance of showers
−15° on Nov. 14, 1959, the coldest reading for this week of the year since 1888. Next is −13° in 1916.
Blackhawk’s center stands about 3,500 ft above sea level. Within three miles the land runs from 3,370 ft to 4,360 ft, a difference of 990 ft: steep hill country. The highest named summit within 15 miles is Scruton Mountain, about 5,890 ft, 13 miles southwest.
Under the town center the state geologic map shows Spearfish Formation (shale, siltstone, sandstone), from the Permian to Early Triassic, 247 to 260 million years old.
The section below crosses 22 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, siltstone, shale. Age: Late Pennsylvanian to Permian, 273 to 307 million years old. About 3 mi of the line.
Coarse-detrital, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Quartzite, schist. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Shale, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Coarse-detrital, clay. Age: Quaternary, less than 2.6 million years old. About 1 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 16 smaller units along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Blackhawk reaches the Gulf of America by way of Boxelder Creek, the Cheyenne, the Missouri and the Mississippi: about 2,520 river miles.
Lakes on the way: Lake Oahe, Lake Sharpe, Lake Francis Case and Lewis and Clark Lake.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Blackhawk; river miles along the main stem, rounded.
Blackhawk has a dry-winter hot-summer continental climate. Summer afternoons average 84° in July; winter nights fall to about 16° in January. A normal year brings about 54 inches of snow; with the rain, that comes to about 20 inches of water.
On November 14 Blackhawk normally reaches 48° and falls to 27°. The record high is 79°, in 1894; the record low −15°, in 1959. The most rain on this date, 0.67 in, fell in 1956.
Normals 1991–2020 and records since 1888 from the Rapid City Downtown Area threaded record (Rapid City Wfo, 7 miles southeast, 120 ft lower). NOAA, through RCC-ACIS.
