Help identify and catalog the trees in Philadelphia's urban forest! PhillyTreeMap is an open-source, web-based map database of trees in the greater 13-county 3-state Philadelphia region. The wiki-style database enables non-profits, government, volunteer organizations, and the general public to collaboratively create an accurate and informative inventory of the trees in their communities. The project was funded by a USDA Small Business Innovation Research Grant and is in support of the Philadelphia Parks & Recreation's 30% tree canopy goal and the Pennsylvania Horticultural Society's "Plant One Million" campaign. As more trees are added to the database, PhillyTreeMap uses the iTree software from the USDA Forest Service to calculate the environmental impact of the region's urban forest. So get outside and add some trees!