Which country won the first Davis Cup in 1900?

The United States won the first Davis Cup in 1900.

The inaugural competition was then called the International Lawn Tennis Challenge. It was staged at the Longwood Cricket Club in Boston, where the United States faced the British Isles. The American team won the tie 3–0, taking the first three matches and claiming the trophy.

The event grew from a challenge proposed by members of Harvard University’s tennis team. Dwight F. Davis helped organize the contest and purchased a sterling-silver trophy, which later gave the competition its familiar name. Davis also played for the winning American side.

This first edition was a small contest between two teams, not the large international tournament associated with the modern Davis Cup. The competition expanded to additional nations during the following years, and Australasia became the first winner from outside the United States and Britain in 1907. A frequent mix-up is calling the 1900 event the “Davis Cup” in its original official title; that name became standard later, although the historical answer remains the United States.