What surface has the US Open been played on since 1978?

The US Open has been played on hard courts since 1978.

That year, the tournament moved to the newly opened USTA National Tennis Center in Flushing Meadows, Queens, and changed from the Har-Tru clay courts used in Forest Hills to a hard-court surface. The change made the US Open the first Grand Slam tournament played on a hard court at that time.

The exact court material and brand have changed. The facility originally used DecoTurf, a cushioned acrylic system, before the courts were resurfaced with Laykold in 2020. Both are hard-court systems, so the answer remains hard court even though the manufacturer and playing characteristics have evolved.

This history is easy to confuse with the other Grand Slam tournaments: the Australian Open is also played on hard courts, Wimbledon uses grass, and the French Open is played on clay. The US Open's modern hard-court identity dates to its 1978 move to Queens.