PlainLakes

Assessed acreage ranking · EPA ATTAINS

Largest lakes in the U.S.

Ranked by the acreage states attached to each lake-type assessment unit in EPA ATTAINS, the federal system holding the Integrated Report decisions states file under Clean Water Act sections 303(d) and 305(b) (reporting cycles 1987-2026). Assessed acreage is the regulatory unit's size, which can differ from a lake's full surface area, and multi-state lakes appear once per state assessment unit. Where a state files one lake as several nested units, each named unit is listed separately.

13,182,720
#1: Superior (acres)
50
Ranked waterbodies
46,036,500
Acres carrying a verdict

This ranking in one line

Superior in MN is the largest lake-type assessment unit in ATTAINS at 20,598 square miles (13,182,720 acres), with an overall status of Not Supporting and 2 listed impairment causes.

#1
Superior, MN
Assessed area
20,598 square miles (13,182,720 acres)
Status
Not Supporting

How large is large? The top-50 cutoff vs every ranked lake

Assessed acreage distribution across ATTAINS lake-type units, counting a state’s repeated filings of one water once

56,487 Top 1% larger than 99%+ of 38,628 lakes

lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value

Source EPA ATTAINS · Reporting cycles 1987–2026

Top 10 largest assessed lake units

Each bar links to that waterbody's assessment record

  1. 1
    Superior (MN) 13,182,720 acres
    Not Supporting
  2. 2
    Lake Huron (Michigan Jurisdiction) (MI) 5,815,360 acres
    Not Supporting
  3. 3
    Lake Michigan South of Frankfort (Michigan Jurisdiction) (MI) 5,665,920 acres
    Not Supporting
  4. 4
    Lake Erie Central Basin Open Water (>3m) (OH) 1,628,787 acres
    Not Supporting
  5. 5
    Iliamna Lake (AK) 960,000 acres
    Not Assessed
  6. 6
    Gilbert Bay (UT) 559,424 acres
    Fully Supporting
  7. 7
    Gunnison Bay (UT) 384,588 acres
    Not Assessed
  8. 8
    Lake Erie Western Basin Open Water (>3m) (OH) 337,472 acres
    Not Supporting
  9. 9
    Lake Sakakawea (ND) 318,821 acres
    Not Supporting
  10. 10
    Lake of the Woods (MN) 301,348 acres
    Not Supporting

Source EPA ATTAINS · Reporting cycles 1987–2026

Data updated 2026-08-17

According to the U.S. Environmental Protection Agency's ATTAINS program, 60,590 lake-type waterbodies carry filed assessment records nationwide, and this ranking orders the 50 largest by the assessed acreage each state attached to its assessment unit in the August 2026 extract. See our methodology for reporting-unit limits, multi-state splits, and refresh cadence.

Assessment verdicts across the 50 largest

Latest overall status filed for each ranked assessment unit

units

What this shows 32 of the 50 largest assessed lake units carry a Not Supporting verdict, and 8 carry no definitive verdict at all, so size does not drive assessment depth.

Source EPA ATTAINS As of Reporting cycles 1987–2026
64 N

Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.

Share of the 50 largest assessed lake units carrying a Not Supporting verdict

Every row

Full ranking

Download CSV
# Name Assessed acres
1 Superior (MN) Not Supporting 13,182,720
2 Lake Huron (Michigan Jurisdiction) (MI) Not Supporting 5,815,360
3 Lake Michigan South of Frankfort (Michigan Jurisdiction) (MI) Not Supporting 5,665,920
4 Lake Erie Central Basin Open Water (>3m) (OH) Not Supporting 1,628,787
5 Iliamna Lake (AK) Largest of 2 assessment units the state files for this water Not Assessed 960,000
6 Gilbert Bay (UT) Fully Supporting 559,424
7 Gunnison Bay (UT) Not Assessed 384,588
8 Lake Erie Western Basin Open Water (>3m) (OH) Not Supporting 337,472
9 Lake Sakakawea (ND) Not Supporting 318,821
10 Lake of the Woods (MN) Largest of 2 assessment units the state files for this water Not Supporting 301,348
11 Fort Peck Reservoir (MT) Not Supporting 233,296
12 Salton Sea (CA) Not Supporting 233,045
13 Lake Erie Sandusky Basin Open Water (>3m) (OH) Not Supporting 231,494
14 Toledo Bend Reservoir-From Texas-Louisiana state line to Toledo Bend Dam (LA) Not Supporting 165,487
15 Red (Lower Red) (MN) Not reported 164,699
16 Lower Red Lake (MN) Fully Supporting 164,689
17 Lake Michigan (Not Indexed) (Salmonid) (Osrw) (IN) Not Supporting 154,176
18 Lake Powell (UT) Fully Supporting 149,885
19 Lake Mead (NV) Fully Supporting 147,392
20 Lake Winnebago (WI) Not Supporting 131,942
21 St. Marys River (MI) Largest of 2 assessment units the state files for this water Not Supporting 129,983
22 Mille Lacs (MN) Not Supporting 128,076
23 Lake Michigan Nearshore (IL) Not Supporting 125,440
24 Lake Tahoe (NV) Not Supporting 122,902
25 Red (Upper Red) (MN) Not Supporting 119,279
26 Upper Red Lake (MN) Fully Supporting 118,943
27 Lake St. Clair (Michigan Jurisdiction) (MI) Not Supporting 103,616
28 Devils Lake (ND) Not Supporting 102,385
29 Leech (Main Basin) (MN) Not Supporting 101,949
30 Kentucky Reservoir (TN) Fully Supporting 99,500
31 Goose Lake (OR) Not reported 93,152
32 Utah Lake other than Provo Bay (UT) Not Supporting 87,984
33 Lake Superior (MN) Fully Supporting 86,000
34 Tahoe, Lake (CA) Not Supporting 84,092
35 Pend Oreille Lake (ID) Not Supporting 80,829
36 Moosehead Lake (ME) Fully Supporting 79,454
37 Farmington Bay (UT) Not Assessed 77,243
38 Lake Okeechobee (FL) Largest of 9 assessment units the state files for this water Not Supporting 76,101
39 Malheur Slough (OR) Not Supporting 73,544
40 Bear River Bay (UT) Not Assessed 71,681
41 Lake Erie (Michigan Jurisdiction) (MI) Not Supporting 71,680
42 Clarks Hill Lake (GA) Fully Supporting 69,999
43 Lake Oahe (ND) Fully Supporting 68,123
44 Goose Lake (Modoc County) (CA) Not reported 62,385
45 Upper Klamath Lake (OR) Not Supporting 62,130
46 Lake of the Ozarks (MO) Not Supporting 59,520
47 Kenai Lake (AK) Not Assessed 57,618
48 Flathead Lake (MT) Not Supporting 57,305
49 Champ-Northeast Arm (VT) Largest of 3 assessment units the state files for this water Not Supporting 57,022
50 White Lake (LA) Not Supporting 56,487

Ordered by the size filed for each assessment unit. States file this figure in acres or in square miles; square-mile filings are converted at 640 acres per square mile and each record page shows the state’s own number. Units filed only as a shoreline length in miles are a different quantity and are not ranked here. Border lakes (for example the Great Lakes) are assessed separately by each adjoining state, so a Great Lakes row is one state's jurisdictional unit, not the whole lake.

Reading this ranking

  • A big assessed acreage means a big regulatory unit, not necessarily the whole lake; border lakes are split across state units. Methodology
  • Check any ranked lake’s designated-use verdicts and causes on its record page. Browse waterbodies
  • For share-based state comparisons with sample floors, see states by impaired share. State shares

Rankings order reported source data; they are not endorsements or safety determinations.

Rankings are computed from state assessment decisions in EPA's ATTAINS system and USGS National Water Information System daily values; the ordering metric and any exclusion floor are stated above the table, no number is typed in by an editor. Ranking recomputed from the full ingested ATTAINS lake-type universe on every data refresh. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.