On July 24, members of Emerald Cities Collaborative joined the U.S. Green Building Council and over 1,250 organizations in a sign-on letter campaign in support of the U.S. General Services Administration's continued use of Leadership in Energy and Environmental Design (LEED). LEED is the most widely used high-performance building rating system in the United States, and provides building owners and operators a concise framework for identifying and implementing practical and measurable green building design, construction, operations and maintenance solutions.