Johnson County, Illinois is one of the more forest-oriented counties in this map set. Forest accounts for 47.01% of the 2025 land-cover summary, while agriculture covers 38.28%. Developed land and wetlands each make up 6.60%, and water accounts for 0.94%. Broad wooded areas dominate much of the north, east, and central interior, while agricultural openings become more common toward the south and southwest.
This page includes four map views: overall land cover, forest and farmland, impervious/developed land, and 1985–2025 class differences. The WebP maps can be viewed directly here, and the four original JPG maps are available together in one download. The set is designed to separate present-day surface cover from hard-surface concentration and from historical classification differences.
Table of Contents
Forest forms the broadest cover, while agricultural openings become larger toward the south
Dark green forest is the most extensive color on the general 2025 land-cover map. Large wooded blocks occupy the north-central and northeastern sections, continue through parts of the east, and reappear in broad patches across the middle and southeast. Agriculture is the second-largest class at 38.28%, but it is distributed differently. Yellow farm cover is more continuous across the southern and southwestern parts of the county and appears as smaller openings within the forest farther north.
The north is not uniformly wooded. Farm patches, developed lines, wetland areas, and small water features interrupt the forest in several places. The northwest contains a noticeable developed concentration surrounded by agriculture and forest. Near the north-central area, water and wetlands appear within a broader wooded setting. The northeast, by contrast, contains some of the more continuous forest cover on the map.
Farther south, the relationship becomes more mixed. Agriculture expands across the southwest and southern edge, but wooded strips repeatedly divide the farm areas. A central-southern developed cluster sits where several road lines meet, with fields and forest close to its edges. This pattern makes Johnson County look less like a simple north-south split and more like a patchwork whose dominant class changes from one local area to another.
Wetlands are a major secondary feature, matching developed land at 6.60%
Wetlands cover 6.60% of the county, the same share as developed land. Teal patches are especially visible in the west-central and southwest areas, along the east and southeast, and near water in the north-central section. Some wetlands are embedded within forest, while others sit along agricultural edges. Their spread across several parts of the county makes them important to the overall pattern even though they are not the dominant class.
Water accounts for only 0.94%, but blue features appear in several distinct places. The clearest examples include water near the north-central portion, smaller pieces in the west and southwest, and narrow blue areas toward the southeast. Because water often lies next to wetlands and forest, it is more informative to read these classes together than to focus on the water percentage alone.
The forest-and-farmland map makes the wooded north and agricultural south easier to compare
The forest-and-farmland view reduces the visual emphasis on developed land and makes Johnson County’s two largest cover types easier to follow. Forest occupies broad areas across the north-central, northeast, east, and parts of the middle. Agriculture becomes more continuous across the south and southwest, while smaller farm openings remain scattered within wooded areas farther north.
The southwest is particularly useful for comparing the two classes because large yellow fields sit beside thick green forest bands and wetland patches. In the central and southeastern parts of the county, fields and woods form smaller interlocking pieces. The northeast contains broader forest with fewer large agricultural openings. These differences explain why a single countywide percentage cannot fully describe how the land-cover classes are arranged.
Hard surfaces remain concentrated in a few settlement nodes and road corridors
Developed land makes up 6.60% of the 2025 summary. The strongest developed clusters appear in the northwest and near the central-southern part of the county, with smaller concentrations in the southwest, west-central area, and east. Thin developed lines connect these nodes along roads. Between them, large areas remain forested or agricultural rather than continuously built up.
Impervious surface is a narrower measure focused on hard materials such as pavement, parking areas, and rooftops. Johnson County has a mean impervious value of 1.21%, and only 0.37% of the county reaches 50% impervious or greater. The gap between 6.60% developed land and 1.21% mean impervious cover reflects the fact that developed land-cover classes can include lawns, trees, soil, and other permeable surfaces.
The impervious map makes the northwest cluster and the central-southern cluster stand out most clearly. A diagonal road corridor crosses from the northwest toward the center, and another strong road line continues southeast from the central node. Smaller dark patches appear in several outlying places, but most forest and farm areas remain very light on the map.
The 12.55% 1985–2025 class difference combines several types of mapped change
Johnson County has a 12.55% overall class-difference value between 1985 and 2025. The map summary identifies 1.06% as classified to developed, 1.29% as forest loss, 1.51% as agricultural loss, and 8.54% as other class difference. Because the “other” category is the largest component, the countywide total cannot be interpreted as a simple measure of development growth, forest clearing, or farmland loss.
Purple other-class differences are spread across much of the south, center, and east, with additional small patches in the north. Red developed differences appear most clearly near present-day settlement nodes and road corridors. Forest-loss and agricultural-loss colors occur as scattered patches of different sizes rather than as one broad conversion front.
Using the four maps together separates present cover, field-forest balance, built surfaces, and historical comparison
The general land cover map is the best starting point for a countywide overview because it shows forest, agriculture, developed land, wetlands, and water together. It makes the forest-dominant north and east, the larger southern farm openings, and the dispersed wetland pattern visible in one frame. The forest-and-farmland map then simplifies the comparison between the two largest classes.
Raster resolution and observation year matter along narrow roads, wetland edges, and small farm openings
Annual NLCD products are commonly represented with roughly 30-meter raster cells. A raster divides the ground into a grid and assigns each cell a representative class or value. Where one cell contains more than one surface—such as forest beside cropland, wetland beside water, or a road through vegetation—the map may simplify that mixed ground into one classification.
This limitation matters in Johnson County because many forest-farm boundaries are irregular, road lines are narrow, and wetland patches can have complex edges. The mapped shapes should not be treated as parcel surveys. Forest colors do not identify ownership or protected status, wetland colors do not establish legal wetland limits, and developed classes do not define zoning.
Frequently Asked Questions
What is the largest 2025 land-cover class in Johnson County?
Forest is the largest at 47.01%, followed by agriculture at 38.28%. Forest is broadest across much of the north and east, while larger agricultural openings appear toward the south and southwest.
Where are the county’s 6.60% wetlands most visible?
Larger wetland patches appear in the west-central and southwest areas, on the east and southeast sides, and around water in the north-central part of the county. They are land-cover classes rather than legal wetland boundaries.
Does the 12.55% 1985–2025 class difference equal physical land-use change?
Not necessarily. Real change may be included, but imagery, vegetation, moisture, classification methods, and mixed pixels can also affect the comparison. Other class difference accounts for 8.54%.
Map File Information
The download combines four original JPG maps for Johnson County: 2025 land cover, forest and farmland, impervious/developed land, and the 1985–2025 land-cover class comparison.
- Included Versions: Land Cover Map, Forest & Farmland Map, Impervious/Developed Land Map, and 1985–2025 Land Cover Change Map
- File Type: One ZIP containing four JPG files
- Intended Use: forest/agriculture comparison, wetland and water review, built-surface patterns, class-change reference, teaching, and presentations
Related Maps
- Adams County Illinois Land Cover Map
- Alexander County Illinois Land Cover Map
- Bond County Illinois Land Cover Map
Sources and references
- MRLC Annual NLCD Data – official access point for Annual NLCD land-cover and impervious-surface products.
- USGS Annual NLCD Land Cover Classification – official documentation for land-cover classes and raster interpretation.
- U.S. Census Bureau TIGER/Line Shapefiles – official geographic boundary source for Johnson County.
Green Map creates custom-edited map images using open geographic data sources such as geoBoundaries, Natural Earth, OpenStreetMap, and government open data.
These maps are edited visual materials, not raw data files, and are provided for education, documents, presentations, and graphic reference.
