| Iowa Natural Heritage FoundationDes Moines | Form 990 | $53,249,669FY2025 |
| Greater Des Moines Botanical GardenDes Moines | Form 990 | $11,844,203FY2025 |
| Iowa Confluence Water TrailsDes Moines | Form 990 | $10,430,095FY2025 |
| Conservation Foundation of Dickinson CountyOkoboji | Form 990 | $6,435,876FY2024 |
| Water Professionals InternationalUrbandale | Form 990 | $3,674,889FY2025 |
| Trees Forever IncMarion | Form 990 | $3,658,423FY2025 |
| Iowa Agriculture Water AllianceAnkeny | Form 990 | $3,396,695FY2025 |
| Talent Collective DSMDes Moines | Form 990 | $2,902,727FY2025 |
| The Spirit of OkobojiOkoboji | Form 990 | $2,566,371FY2025 |
| Pathfinders Resource Conservation and Development Area IncFairfield | Form 990 | $2,405,832FY2025 |
| Indian Creek Nature CenterCedar Rapids | Form 990 | $1,919,146FY2025 |
| Deb & Jeff Hansen FoundationWest Des Moines | Form 990 | $1,897,589FY2024 |
| Iowa Environmental CouncilDes Moines | Form 990 | $1,883,599FY2024 |
| Clean Energy Districts of IowaDecorah | Form 990 | $1,737,594FY2025 |
| Iowa Valley Resource Conservation & DevelopmentAmana | Form 990 | $1,625,086FY2025 |
| Nahant Marsh Education CenterDavenport | Form 990 | $1,440,067FY2025 |
| Soil and Water Conservation SocietyAnkeny | Form 990 | $1,237,618FY2025 |
| Resource Conservation and Development for Northeast Iowa IncPostville | Form 990 | $1,184,936FY2025 |
| Agricultures Clean Water AllianceAnkeny | Form 990 | $1,178,388FY2026 |
| Iowa Nutrient Research and Education CouncilDes Moines | Form 990 | $1,104,163FY2025 |
| Iowa Arboretum IncMadrid | Form 990 | $1,061,103FY2025 |
| Sustainable Iowa Land TrustWest Branch | Form 990 | $945,139FY2025 |
| Mason City FoundationMason City | Form 990 | $909,263FY2024 |
| Green Schools National Network IncIowa City | Form 990 | $791,499FY2025 |
| Golden Hills Resource Conservation and Development AreaOakland | Form 990 | $783,865FY2024 |
| Build a Better BelmondBelmond | Form 990 | $731,768FY2025 |
| Dubuque Arboretum Association IncDubuque | Form 990 | $659,933FY2025 |
| William G Stowe Memorial FoundationDes Moines | Form 990 | $618,495FY2025 |
| Keep Iowa BeautifulJohnston | Form 990 | $614,213FY2025 |
| Iowa Business for Clean EnergyWest Des Moines | Form 990 | $526,784FY2024 |
| Newton Arboretum & Botanical Gardens IncNewton | Form 990 | $505,957FY2025 |
| Southwest Iowa Nature Trails Project IncImogene | Form 990 | $352,427FY2024 |
| Iowa Storm Water Education PartnershipDes Moines | Form 990 | $304,427FY2025 |
| Cedar Valley Arboretum & Botanic GardensWaterloo | Form 990 | $300,377FY2024 |
| Clinton County Conservation Foundation IncGrand Mound | Form 990 | $297,780FY2024 |
| Iowa Great Lakes FoundationDes Moines | Form 990 | $279,697FY2024 |
| Iowa Great Lakes BeautificationOkoboji | Form 990 | $273,932FY2025 |
| Eastern Iowa Conservation Foundation LtdDubuque | Form 990 | $271,411FY2025 |
| Energy Association of Iowa SchoolsCreston | Form 990 | $237,750FY2025 |
| Izaak Walton League of America IncNewton | Form 990 | $237,549FY2025 |
| Iowa Interfaith Power and Light Iowa Faith and Climate NetworkDes Moines | Form 990 | $236,374FY2025 |
| Rathbun Land and Water Alliance IncCenterville | Form 990 | $225,659FY2025 |
| Des Moines Chapter of the Izaak Walton League of AmericaDes Moines | Form 990 | $218,955FY2025 |
| Sioux County Conservation FoundationHawarden | Form 990 | $213,219FY2024 |
| Friends of Winnebago County Conservation Foundation IncForest City | Form 990 | $203,786FY2023 |
| Holiday Lights at the LakeCoralville | Form 990 | $184,680FY2024 |
| Solid Waste Association of North America IncStorm Lake | Form 990-EZ | $175,619FY2026 |
| Winneshiek Energy DistrictDecorah | Form 990-EZ | $169,889FY2025 |
| N-Compass IncMarion | Form 990-EZ | $169,014FY2025 |
| Izaak Walton League of America IncCedar Rapids | Form 990 | $161,761FY2024 |