From its beginning, Mercer Island Sister City Association has been a member of  Sister Cities International . SCI grew out of an effort to heal the wounds of World War II. It was established in 1956 by President Dwight D. Eisenhower, who envisioned a way for U.S. cities to create formal partnerships with foreign cities. Municipality to municipality, cities could exchange information and ideas in order to develop friendships and deepen cultural understanding.

This vision sparked the creation of SCI, which today includes more than 500 U.S. cities with relationships in 145 countries – a total of some 2,000 municipal partnerships. Each year, thousands of citizen diplomats, young and old, represent the United States around the world, promoting democracy and understanding.

The mission of SCI is to promote peace through mutual respect, understanding and cooperation – one individual, one community at a time.
It is a nonprofit citizen diplomacy network that creates and strengthens partnerships between the U.S. and international communities. SCI strives to build global cooperation at the municipal level, promote cultural understanding and stimulate economic development.