The Cincinnati Open switched from clay courts to hard courts in 1979.
The tournament was played on clay from its founding in 1899 through 1978. In 1979, it moved to Mason, Ohio, where a permanent stadium was built, and the surface changed from Har-Tru clay to hard court. The event also shifted its calendar position to two weeks before the US Open, a more prominent place in the professional season.
The 2026 Cincinnati Open was therefore part of a hard-court tradition lasting more than four decades. Surface history can cause confusion because the tournament's earliest matches were played on what contemporary reports described as crushed brick dust. The present-day event is an outdoor hard-court ATP Masters 1000 and WTA 1000 tournament.