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What is left of Ohio's wetlands

1,233 of 1,233 Ohio ZIP codes have a figure; the median one has 1.4% of the land.

Open this topic on the map Wetlands by ZIP code

Ohio was once much wetter. Most of its original wetlands, including the Great Black Swamp that covered the northwest corner of the state, were drained through the nineteenth and twentieth centuries into some of the most productive farmland in the country, and roughly a tenth of the original acreage is left. What remains is not spread evenly: the Lake Erie marshes, the swamp forest remnants of the northwest and the glacial kettles of the northeast hold most of it.

This ranks the 25 Ohio ZIP codes with the largest share of their land in a mapped wetland, largest first, from the U.S. Fish and Wildlife Service's National Wetlands Inventory. Ranking by share rather than by acres puts a small marsh-covered ZIP code ahead of a large one holding more acres in total. How much wetland a place has is a separate question from what condition it is in.

Across the state

One dot per ZIP code, colored the way the map colors this topic; larger dots are more populous ZIP codes.

Under 1% of the land (492) 1 to 3% (435) 3 to 7% (210) 7 to 15% (76) 15% or more wetland (20)

The 25 ZIP codes with the most wetland

Highest first; every ZIP code links to its own page.

  1. 44064 · Montville Township and MontvilleGeauga County33.8% of the land
  2. 44450 · Greene Township and North BloomfieldTrumbull County27.5% of the land
  3. 43733 · Valley Township and DerwentGuernsey County27.4% of the land
  4. 44402 · Bristol Township and BristolvilleTrumbull County23.7% of the land
  5. 43452 · Port ClintonOttawa County21.6% of the land
  6. 44613 · BrewsterStark County21.4% of the land
  7. 44285 · Paris Township and WaylandPortage County20.8% of the land
  8. 43805 · Clark Township and BlissfieldCoshocton County19.4% of the land
  9. 44032 · Dorset Township and DorsetAshtabula County19.2% of the land
  10. 43464 · Townsend Township and VickerySandusky County19.1% of the land
  11. 44021 · Burton Township and BurtonGeauga County18.9% of the land
  12. 44099 · Windsor Township and WindsorAshtabula County17.9% of the land
  13. 44428 · Kinsman Township and KinsmanTrumbull County17.4% of the land
  14. 43433 · Portage Township and GypsumOttawa County17.0% of the land
  15. 43449 · Oak HarborOttawa County16.3% of the land
  16. 44076 · Orwell Township and OrwellAshtabula County16.2% of the land
  17. 44085 · Hartsgrove Township and RomeAshtabula County16.1% of the land
  18. 44045 · Grand RiverLake County15.9% of the land
  19. 44093 · Williamsfield Township and WilliamsfieldAshtabula County15.5% of the land
  20. 44003 · Andover Township and AndoverAshtabula County15.4% of the land
  21. 44491 · Farmington Township and West FarmingtonTrumbull County14.9% of the land
  22. 44062 · Middlefield Township and MiddlefieldGeauga County14.0% of the land
  23. 44047 · JeffersonAshtabula County14.0% of the land
  24. 43616 · OregonLucas County14.0% of the land
  25. 44046 · Huntsburg Township and HuntsburgGeauga County13.3% of the land

How this was measured

The U.S. Fish and Wildlife Service's National Wetlands Inventory for Ohio, mapped from aerial photographs: freshwater marshes (emergent), swamps (forested and shrub) and ponds, clipped to each ZIP, with open lakes and river channels left out. Ohio drained about 90 percent of its original wetlands, so what remains is concentrated in the northwest's Great Black Swamp remnants, the Lake Erie marshes and the glacial kettles of the northeast. Mapped wetlands carry federal and state permit requirements for filling, and they are where the water table sits at the surface. Ohio EPA's vernal pool screening, high-quality wetland list and mitigation sites are noted. Ohio EPA's own wetland assessments add the nearest studied wetland with its ORAM and plant community scores. Where USGS topographic maps marked marsh or swamp, the card gives those acres too.

The ranking is by the share of each ZIP code's land that is mapped wetland, so a small ZIP code on the Lake Erie marshes outranks a large one holding more acres in total.

1,233 of 1,233 ZIP codes have a figure; ZIP codes without one are left off the list, not counted as zero. Ties are broken by ZIP code.

Every ZIP code's own page carries the full detail behind its figure, and the Wetlands topic page ranks the whole state.

Sources

USFWS National Wetlands Inventory, Ohio geodatabase (imagery mostly 2004 to 2007, Lake Erie basin 2021), freshwater wetlands and ponds clipped to each ZIP (lakes and rivers excluded); Ohio EPA potential high-quality vernal pools, high-quality wetland sites and stream and wetland mitigation sites; Ohio EPA Wetland Ecology Group sampling sites with ORAM and VIBI scores; Ohio EPA hydro/Wetlands_USGSTopoMaps (wetland symbols digitized from USGS 7.5-minute topographic maps), clipped to the ZIP.

USFWS wetlands inventory · Ohio EPA GIS services

The figures behind this page are open data: the open JSON, CC BY 4.0 for the compilation. Report a correction.

Cite this page as:

Cracked Buckeye (Open Shower Co), "What is left of Ohio's wetlands", https://crackedbuckeye.com/stories/wetlands-remaining/, built 2026-09-16, accessed [date].

One figure from it:

Cracked Buckeye (Open Shower Co), "What is left of Ohio's wetlands", https://crackedbuckeye.com/stories/wetlands-remaining/, built 2026-09-16, accessed [date]; Wetlands from USFWS wetlands inventory.

How to cite · Report a correction · Built 2026-09-16