Johnson County, IL Elevation & Topographic Map
Elevation
860 ft 260 m720 ft 220 m660 ft 200 m520 ft 160 m390 ft 120 m320 ft 95 m
Contours every 500 ft, bold every 2,500 ft
USGS 3DEP · U.S. Census Bureau
How to use this mapviews, tools and data
- Elevation
- Ground colored by height from green (lowest) to white (highest), with contour lines every 40–500 ft (USGS data).
- Satellite
- A 2016 satellite photo at 33 ft (10 m) detail; contours off.
- 3D
- Tilt and turn the terrain; hills are raised 1.5×, or set ×1 for true height.
- Click or tap anywhere
- The exact elevation of that spot in ft and m.
- Measure
- Pick two points for the climb, descent and grade along a straight line.
- County area
- Fades everything outside the official county boundary (US Census).
Elevation Data
Johnson County averages about 500 ft (155 m) above sea level across all its land. Its ground runs from 320 ft on the south side to 860 ft on the northwest side.
Average elevation
500 ft 155 m
all land inside the county
Highest
860 ft 260 m
on the northwest side
Lowest
320 ft 95 m
on the south side
Johnson County spans about 540 ft of height, so no single spot tells the whole story. The ruler shows where most of its land lies, and where the other numbers you'll see come from.
| Figure | Elevation |
|---|---|
| Average of all land | 500 ft155 m |
| Highest point Inside the county, on the northwest side | 860 ft260 m |
| Lowest point Inside the county, on the south side | 320 ft95 m |
Elevation profile, south to north
19 mi south to north through Vienna.
Topographic Map
- Location
- County in Illinois, United States
- Population
- 13,320 2024 est.
- Land area
- 343.7 sq mi + 4.9 sq mi water
- Density
- 39 per sq mi
- Time zone
- Central UTC−6 / −5
- Landform region
- Interior Low Plateaus 98%
- Drains to
- Gulf of America
⤓ Download this map
WebP, 1200 × 900. Free to use: credit “ElevationOf.com” with a link to this page.
Sources: U.S. Census Bureau, USGS
Nearby Places
Neighboring counties sharing a border, by average
- Pope County510 ft
- Union County500 ft
- Johnson County500 ft
- Williamson County470 ft
- Saline County420 ft
- Massac County390 ft
- Pulaski County360 ft
Rankings by average elevation
- Counties in Illinois79th highest of 102
- Counties in the United States2,322nd highest of 3,151
Peaks and hills highest inside
- Blue Knob500 ft
- Hairy Hill480 ft
- Island Hill, Johnson County450 ft
How we measure
- Average: every USGS 3DEP bare-earth cell of land inside the Census county boundary (TIGER/Line, Jan 1 2026), weighted equally, on a 1 arc-second (≈100 ft, 30 m) grid. Land means the boundary minus Census area water.
- Highest and lowest: the highest land cell. Lowest: the lowest land cell; coastal ground within 3 ft (1 m) of named tidal water counts as sea level.
- Nearby Places: neighboring counties and rankings use each one's average elevation, on its own grid, the same figure its page shows. Peaks and hills: the highest summits inside the county with at least 980 ft (300 m) of prominence, then the highest federal (GNIS) summits inside it when there are fewer than 5; each is the 3DEP top on a ~7 ft (2 m) window, or the NGS published height when a usable survey mark sits within 160 ft (50 m) of it (shown as published).
- Towns: each town's typical elevation (population-weighted median of its own 2020 blocks at 1 arc-second); a town is listed when any of its 2020 residents live in the county.
- Rounding: computed heights are rounded to 10 ft (5 m), or to 1 ft (1 m) under 100 ft; 3DEP is good to about a meter, not a foot. Published figures (NGS survey heights) are shown as their publisher gives them.
- Datum: North American Vertical Datum of 1988 (NAVD 88). NGS plans to replace NAVD 88 with a new datum (NAPGD2022); heights will then shift slightly.
- Sources: USGS 3DEP, GNIS, Watershed Boundary Dataset and physiographic provinces; U.S. Census Bureau (TIGER boundaries and water, 2020 blocks, 2024 population estimates, county adjacency); NOAA NGS survey heights; BTS time zones. All public domain.