Today marks the first day of the 2018 U.S. Open Tennis Championships, a U.S.T.A. event at Flushing Meadows-Corona Park, Queens. Tennis stars Serena Williams and Rafael Nadal will play on opening night. In fact, eight former U.S. Open champions will play today, Andy Murray, Venus Williams, Svetlana Kuznetsovaand, Sloane Stephens, Juan Martin del Potro, and Stan Wawrinka, in addition Serena Williams and Nadal.

But the U.S. Open was not always as it is today. Here are 10 secrets and fun facts about this illustrious tournament:

1. The U.S. Open Was Originally Played on Grass

It might be hard to imagine today, with the U.S. Open so firmly established in people’s minds as a hard court tournament, buit t was played on grass for almost a century, from 1881 to 1974. The first tournament, held at the Newport Casino in Rhode Island, was hosted by the US National Lawn Tennis Association and was known as the “US National Singles Championship.” This was, by all accounts, more of an upper crust, society event. Until 1886, the tournament was also mens-only. The U.S. Women’s National Singles Championship started in 1887 and was held in Philadelphia at the Philadelphia Cricket Club.