| Company |
City |
State |
| Cabelas | Sidney | Nebraska |
| Cadmus Group | Watertown | Massachusetts |
| CALIBRE | Alexandria | Virginia |
| California Air Resources Board | Sacramento | California |
| California Energy Commission | Sacramento | California |
| California Native Plant Society | Sacramento | California |
| California Native Plant Society | Sacramento | California |
| California Public Utilities Commission | San Francisco | California |
| California State University, Stanislaus | Turlock | CA |
| California Wild Heritage Campaign | Sacramento | California |
| Californians for Alternatives to Toxics | Eureka | California |
| CALSTART | Pasadena | California |
| Camco | Denver | Colorado |
| Canaan Valley Institute | Davis | West Virginia |
| Canon USA | Lake Success | New York |
| Capability Company | Raleigh | North Carolina |
| Capital H Group | Milwaukee | Wisconsin |
| Career Management Group, LLC | East Hanover | New Jersey |
| Cargill, Inc. | Minneapolis | Minnesota |
| Caritas Creek Environmental Education | Occidental | California |
| Carnegie Museum of Natural History, Powdermill Nature Reserve | Rector | Pennsylvania |
| Carolina Raptor Center | Charlotte | North Carolina |
| Carter & Burgess, Inc. | Fort Worth | Texas |
| Cascadia Community College | Bothell | Washington |
| Cascadia Region Green Building Council | Portland | Oregon |
| CB Richard Ellis Group, Inc. | Los Angeles | California |
| CEMML | Fort Collins | Colorado |
| Center for Environmental Management of Military Lands | Fort Collins | Colorado |
| Center for Food Safety | Washington | District of Columbia |
| Center for Food Safety | Washington | District of Columbia |
| Center for Science in the Public Interest | Washington | District of Columbia |
| CGI-AMS | Atlanta | Georgia |
| CH2M HILL | Herndon | Virginia |
| CH2M HILL | Englewood, | Colorado |
| CH2M HILL | Milwaukee | Wisconsin |
| Charles Abbott Associates, Inc. | Mission Viejo | California |
| Charles P. Johnson & Associates, Inc. (CPJ) | Silver Spring | Maryland |
| Charles Stewart Mott Foundation | Flint | Michigan |
| Chelan County PUD | Wenatchee | Washington |
| Chemonics International | Washington | District of Columbia |
| Chippewa Nature Center | Midland | Michigan |
| Christopher A. Joseph & Assoc. | Los Angeles | California |
| Cincinnatus Inc. | Minneapolis | Minnesota |
| CirclePoint | San Francisco | California |
| Citizens for a Healthy Bay | Tacoma | Washington |
| Citizens for a Healthy Bay | Tacoma | Washington |
| City and County of Honolulu | Honolulu | Hawaii |
| City of Alexandria | Alexandria | Virginia |
| City of Atlanta | Atlanta | Georgia |
| City of Aurora | Aurora | Colorado |
| City of Austin, TX | Austin | Texas |
| City of Boulder OSMP | Boulder | Colorado |
| City of Carlsbad | Redwood City | California |
| City of Cedar Hill | Cedar Hill | Texas |
| City of Chula Vista | Chula Vista | California |
| City of Cupertino | Cupertino | California |
| City of Evanston | Chicago | Illinois |
| City of Flagstaff | Peoria | Arizona |
| City of Franklin | Franklin | Tennessee |
| CITY OF IMPERIAL BEACH | IMPERIAL BEACH | California |
| City of Imperial Beach | Imperial Beach | California |
| City of Largo | Largo | Florida |
| City of Long Beach | Long Beach | California |
| City of Los Angeles Environmental Affairs Department | Los Angeles | California |
| City of Milwaukee | Milwaukee | Wisconsin |
| City of Saint Paul | West Saint Paul | Minnesota |
| City of Santa Cruz | Modesto | California |
| City of Scottsdale | Scottsdale | Arizona |
| City of South San Francisco | Redwood City | California |
| City of Sugar Land | Sugar Land | Texas |
| City of Tacoma | Tacoma | Washington |
| Clark Group | Washington | District of Columbia |
| Clarke Mosquito Control | Roselle | Illinois |
| Clean Energy Group, Inc. | Montpelier | Vermont |
| Clean Harbors Environmental Services, Inc. | Wilmington | California |
| Clean Water Action | Boston | Massachusetts |
| Clearpool Education Center | Carmel | New York |
| Clemson University | Pickens | South Carolina |
| Cleveland Metroparks | Cleveland | Ohio |
| Clipper Windpower | Carpinteria | California |
| Clover Park Technical College | Lakewood | Washington |
| Coastal Carolina University | Conway | South Carolina |
| Coastal Carolina University | Conway | South Carolina |
| Cobalt Engineering | Vancouver | British Columbia |
| Coca Cola Enterprises | Atlanta | Georgia |
| Coca-Cola Company | Atlanta | Georgia |
| Coconino County | Flagstaff | Arizona |
| Coeur d'Alene Tribe | Plummer | Idaho |
| Colby College | Waterville | Maine |
| Colby College | Waterville | Maine |
| COLBY COLLEGE | Waterville | Maine |
| Colorado Department of Transportation | Denver | Colorado |
| Colorado Department of Transportation | Denver | Colorado |
| Colorado Division of Wildlife | Denver | Colorado |
| Columbia River Estuary Study Taskforce | Astoria | Oregon |
| Columbia Riverkeeper | Hood River | Oregon |
| Commission for Environmental Cooperation | Montréal | Quebec |
| CONCUR, Inc. | Berkeley | California |
| Conestoga-Rovers & Associates | Depew | New York |
| Confidential | Frankfort | Illinois |
| Confidential | Mill Valley | California |
| Connecticut Fund for the Environment | New Haven | Connecticut |
| Conservation and Environmental Sciences, University of Wisconsin Milwaukee | Milwaukee | Wisconsin |
| Conservation Law Foundation | Boston | Massachusetts |
| Conservation Services Group, Inc | Westborough | Massachusetts |
| Conservation Services Group, Inc. | Westborough | Massachusetts |
| Constructive Technologies Group Inc. | Irvine | California |
| Consultative Group on Biological Diversity | San Francisco | California |
| Cornell Cooperative Extension | Ithaca | New York |
| Cornell Cooperative Extension | Riverhead | New York |
| Corrigan Consulting, Inc. | Houston | Texas |
| Cotton Incorporated | Cary | North Carolina |
| Council for Environmental Education | Houston | Texas |
| Council for Environmental Education | Houston | Texas |
| County of Kauai, Hawaii | Merced | California |
| County of Riverside | Riverside | California |
| County of Sacramento | Sacramento | California |
| County of San Diego | San Diego | California |
| County of San Mateo | Redwood City | California |
| County of San Mateo | Redwood City | California |
| County of Santa Clara, Caliornia | San Jose | California |
| County of Santa Cruz | Santa Cruz | California |
| County of Sonoma | Santa Rosa | California |
| County of Sonoma | Santa Rosa | California |
| Craton Equity Partner | Los Angeles | California |
| Creative Media Agency | Mineola | New York |
| CSA, Ltd. | Fort Worth | Texas |
| CSIRO | Canberra, Australia | International |
| CSIRO Marine Research | Hobart | International |
| CTG Energetics, Inc. | Irvine | California |
| Cuyahoga County Planning Commission | Cleveland | Ohio |
