The Harlem 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.
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Harlem’s center stands about 2,370 ft above sea level. Within three miles the land runs from 2,340 ft to 2,610 ft, a difference of 270 ft: rolling country. The highest named summit within 15 miles is East Butte, about 3,300 ft, 15 miles north.
Under the town center the state geologic map shows Alluvium (gravel, sand, silt), from the Pleistocene to Holocene, less than 1.8 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 28×. 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, shale. Age: Late Cretaceous, 72 to 84 million years old. About 10 mi of the line.
Shale. Age: Late Cretaceous, 72 to 84 million years old. About 10 mi of the line.
Gravel, sand, silt. Age: Pleistocene to Holocene, less than 1.8 million years old. About 5 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Harlem reaches the Gulf of America by way of the Milk River, the Missouri and the Mississippi: about 3,260 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Sharpe and Lake Francis Case.
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 Harlem; river miles along the main stem, rounded.
