The US Open is a Grand Slam tennis tournament held in New York City at the USTA Billie Jean King National Tennis Center in the area of Flushing Meadows. In 1968, this tournament became open to professionals and has been known since then as the US Open. The person who has reached the finals for singles the most in tournament history is Serena Williams. Since 1999, Serena Williams has reached the final ten times and won six titles. The two players who have won the most singles titles, with six titles each, are Serena Williams and Chris Evert.