The Lamar Hunt U.S. Open Cup is the oldest ongoing national soccer competition in the United States, first played in 1914 under the name U.S. Soccer's National Championship. It is a single-elimination tournament open to all amateur and professional soccer teams in the United States, regardless of their affiliation with a league. 

The tournament is named after Lamar Hunt, a pioneer of American soccer who also founded the Kansas City Chiefs and the Dallas Cowboys. The Open Cup is often referred to as the "Nation's Cup" and is considered the most prestigious domestic soccer tournament in the United States.

The Open Cup is divided into several rounds, with the lowest-division teams entering in the early rounds and the top-division teams entering in later rounds. The tournament culminates in a single-match final, which is usually played in September.

The current champions are the New York Red Bulls, who defeated Atlanta United in the 2022 final. The most successful club in Open Cup history is Bethlehem Steel FC, which has won the tournament 5 times.

The Open Cup is a popular event among soccer fans in the United States. It provides an opportunity for smaller clubs to compete against top-flight teams, and it often produces some exciting and unpredictable matches.

The Open Cup is also a great way to promote soccer in the United States and to grow the sport's popularity.

Here are some of the notable moments in the history of the U.S. Open Cup:

In 1967, the amateur team Washington Diplomats defeated the professional team New York City FC in the final. This was the first time that an amateur team had won the Open Cup.

In 1999, the Rochester Rhinos became the first team from outside of the top division to win the Open Cup.

In 2017, the Seattle Sounders defeated the defending champion FC Dallas in the final. This was the Sounders' first Open Cup title.

In 2022, the New York Red Bulls defeated Atlanta United in the final. This was the Red Bulls' second Open Cup title.

The U.S. Open Cup is an important part of American soccer history. It is a tournament that celebrates the diversity of the sport and provides an opportunity for all teams to compete for the ultimate prize. The Open Cup is a great way to experience the excitement of soccer in the United States.