According to United States Department of State, the idea of "twinning" a community with a foreign counterpart is believed to have originated during the World War II. In 1944, the Canadian port city of Vancouver became sister city to the recently liberated Soviet port city of Odessa. Vancouverites sent badly needed reconstruction supplies and held an "Odessa Week" to celebrate Russian and Ukrainian culture.

With the war's end, Europeans in particular embraced cross-border linkages between communities as a means of cultivating mutual understanding and forestalling another armed conflict. Thus, only two years after the conclusion of hostilities between Great Britain and Germany, Bristol, England, and Hanover, Germany, were twinned. The Bristolians sent food and clothing and the cities initiated a series of education exchanges. Today, an estimated 25,000 residents of the two cities have visited their sister city and contributed to a lasting international friendship.

In 1956, President Eisenhower initiated the U.S. “People-to-People” program, forerunner of the U.S. sister-city movement. "If we are going to take advantage of the assumption that all people want peace, then the problem is for people to get together and to leap governments … to work out not one method but thousands of methods by which people can gradually learn a little bit more of each other," Eisenhower said.

In 1967, Sister Cities International (SCI) was founded. The nonprofit citizen diplomacy network encourages sister-city partnerships between U.S. and international communities and works to "promote peace through mutual respect, understanding and cooperation -- one individual, one community at a time."

Among SCI’s programs is Wheelchairs for Peace, a five-year effort to distribute wheelchairs to sister-city communities throughout the world. Through this initiative, American communities have supplied wheelchairs to their sister cities in China, Morocco, Peru, Moldova, Poland, Mexico, Lebanon, Mali and South Africa, among others.

American towns and cities help their sister cities in a number of ways. Engineers from Portland, Maine, for example, have worked to increase and improve the potable water supply at a hospital in Portland’s sister city in Haiti, Cap-Haitien.  Denver donated a septic truck to Axum, Ethiopia, where lack of a sewer system has led to sanitation problems. Fort Lauderdale, Florida, has spearheaded an Internet access and training center in Agogo, Ghana.

The sister-city movement today reaches 2,500 communities in 134 countries.