The following is a list of picnic areas that are accessible to visitors with disabilities.
Alabama
Horseshoe Bend National Military Park
Arizona
Grand Canyon National Park
Saguaro National Park
California
Yosemite National Park
Colorado
Colorado National Monument
The Devils Kitchen Picnic Area and visitor center picnic areas are accessible.
Great Sand Dunes National Park and Preserve
Rocky Mountain National Park
Florida
Gulf Islands National Seashore
All picnic pavilions are accessible in the Florida District and the Mississippi District. Many outdoor picnic tables are accessible for visitors using wheelchairs.
Hawaii
Haleakala National Park
Indiana
Indiana Dunes National Lakeshore
Iowa
Herbert Hoover National Historic Site
Kansas
Tallgrass Prairie National Preserve
Maine
Acadia National Park
New Mexico
Fort Union National Monument
North Dakota
Knife River Indian Villages National Historic Site
Pennsylvania
Allegheny Portage Railroad National Historic Site
Johnstown Flood National Memorial
Steamtown National Historic Site (seasonally)
Utah
Arches National Park
Virginia
Shenandoah National Park
Washington
Olympic National Park
Wisconsin
St. Croix National Scenic Riverway
Access Your National Parks: A guide to accessibility programs, National Park Service
http://www.nps.gov/access/index.htm