What US championship event was introduced in 1892?

The mixed doubles championship was introduced in 1892. It joined the established singles and doubles competitions during the early years of what is now the US Open.

The 1892 U.S. National Championships were split between Newport, Rhode Island, and Philadelphia. The men's events were held at the Newport Casino, while the women's competitions and the new mixed doubles event took place at the Philadelphia Cricket Club.

Mabel Cahill and Clarence Hobart won the inaugural mixed doubles title, defeating Elisabeth Moore and Rodmond V. Beach. The event remains part of the tournament's five senior championships, alongside men's singles, women's singles, men's doubles, and women's doubles. Wheelchair and junior events are important modern additions, but they were introduced much later and are not the answer to this historical question.