In July 2026, the Office of the City of Yokohama Representative to the Americas took part in the 70th Anniversary Homecoming event run by Sister Cities International in Washington, D.C., a celebration marking seventy years since the organization’s founding. Established in the United States in 1956, Sister Cities International is an international organization dedicated to promoting sister city relationships across the globe. This milestone event brought together municipal representatives and sister city partners from around the world to celebrate seven decades of citizen diplomacy and to explore, through shared stories, partnerships, and diverse exchanges, a new era of international connection.

As part of the program, the Embassy of Japan in the United States hosted a Welcome Reception on July 23. There, the Office of the City of Yokohama Representative to the Americas promoted GREEN×EXPO 2027 and used the occasion to engage with representatives of overseas municipalities and sister city organizations, sharing Yokohama’s approach to sustainable urban development along with its broader international initiatives.

Sister city relationships rest on more than exchanges between local governments alone; they are sustained by the continued involvement of citizens, educational institutions, businesses, and community organizations. It is this kind of grassroots engagement that builds mutual understanding and trust over time, opening the way for cooperation across fields as varied as education, culture, business, innovation, and the environment, while also laying important groundwork for broader international cooperation. The anniversary event was thus an occasion not only to mark seventy years of Sister Cities International, but to underscore how essential it is to carry these relationships of trust forward to future generations.

Among the partnerships represented was Yokohama’s own relationship with San Diego, established in 1957 and now approaching its 70th anniversary in 2027. Formed just one year after Sister Cities International itself was founded, the partnership has grown over the decades to encompass education, culture, business, and the environment, building a deep and enduring relationship between the two cities.

With San Diego’s 70th anniversary and the hosting of GREEN×EXPO 2027 both falling in the same year, 2027 will be a significant one for Yokohama. As the city’s representative office in the Americas, the office will continue drawing on the international network it has built to deepen collaboration with partners across the region, build momentum toward GREEN×EXPO 2027, and strengthen Yokohama’s presence on the international stage.