From their mission statement:
The Mission of the American Community Gardening Association is to build community by increasing and enhancing community gardening and greening across the United States and Canada.
The American Community Gardening Association (ACGA) is a bi-national nonprofit membership organization of professionals, volunteers and supporters of community greening in urban and rural communities. The Association recognizes that community gardening improves people’s quality of life by providing a catalyst for neighborhood and community development, stimulating social interaction, encouraging self-reliance, beautifying neighborhoods, producing nutritious food, reducing family food budgets, conserving resources and creating opportunities for recreation, exercise, therapy and education...
The American Community Gardening Association has been around since 1979 and is dedicated to providing educational resources and support to community gardeners. One of the ways the American Community Gardening Association helps individual gardeners is by writing letters of support when your community garden is threatened because of differences with people or groups such as your landlord, neighbors or local government officials. You can join and place your community garden or find other community gardens on the local harvest map.