The Hillsboro 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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−3° on Nov. 17, 1959, the coldest reading for this week of the year since 1893. Next is 1° in 1901.
Hillsboro’s center stands about 730 ft above sea level. Within three miles the land runs from 600 ft to 750 ft, a difference of 150 ft: gently rolling country.
Under the town center the state geologic map shows St. Louis and Pella Formations (dolostone, limestone), from the Middle Mississippian to Late Mississippian, 324 to 347 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 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Dolostone, limestone. Age: Middle Mississippian to Late Mississippian, 324 to 347 million years old. About 12 mi of the line.
Shale, sandstone, siltstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 9 mi of the line.
Dolostone, limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 3 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 Hillsboro reaches the Gulf of America by way of Cedar Creek, the Skunk and the Mississippi: about 1,430 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hillsboro; river miles along the main stem, rounded.
Hillsboro has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 13° in January. A normal year brings about 25 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Hillsboro normally reaches 50° and falls to 29°. The record high is 74°, in 1990; the record low 3°, in 2019. The most rain on this date, 1.40 in, fell in 1899.
Normals 1991–2020 and records since 1893 at Mount Pleasant 1 SW, 11 miles northeast. NOAA, through RCC-ACIS.
