Oldest Sister City Relationship Established Between Toledo, Ohio and Toledo, Spain. Although many communities site evidence of exchanges or other activities, Sister Cities International has verified that officials from Toledo, Ohio, and Toledo, Spain signed a twinning document in 1931.

The oldest "official" sister city relationship in the United States is between Toledo, Ohio, and Toledo, Spain, which was formalized in 1931. This was the first documented case of "town twinning" in North America. The relationship was created to foster cultural exchange and mutual understanding between the two namesake cities. Following World War II, the movement expanded significantly with the founding of Sister Cities International by President Dwight D. Eisenhower in 1956, which aimed to use community-level diplomacy to prevent future global conflicts. Today, in 2026, the two Toledos still maintain active ties, and the relationship is celebrated as the pioneer of a global network that now includes thousands of partnerships between U.S. cities and international municipalities across every continent.