Women first participated at the 1900 Games in Paris in tennis, Golf, and croquet. The first woman Olympic champion was Charlotte Cooper of Great Britain in ladies singles tennis.
Three sports that I know of at one time allowed women to compete against men. Sailing at one time had several events open to men and women but in recent years has created separate events . Likewise shooting used to be open but they too have created separate events. Equestrian is the only current sport open to both sexes. Both shooting and equestrian have had women win gold medals competing against men. In the Winter Games the rules for luge allow for the doubles event to have women compete but I don't think this has happened as of yet.
That is the 10k Open Water event that debuted at the 2008 Games in Beijing. Lara Ilchenko of Russia won the gold medal in a time of 59 minutes, 27.7 seconds. Prior to the 2008 Olympics, the longest swimming event for women was the 800 meter freestyle.
As far as the modern Olympics go, swimming events have been a part since the first modern Games in 1896.
Every Olympic has a new event added to it, whether it a completely new sport, event, or existing event which allows another sex to compete in it. Here are some example of the past few Olympics sports addition. 2006 Turin added Snowboard Cross. 2008 Beijing added Open Water Swimming and BMX racing. 2010 Vancouver added Ski Cross. 2012 London will add Women's Boxing. 2014 Sochi will add Women's Ski Jumping. 2016 Rio will add Golf and Rogby.
1895The US Open was first held in 1895. It is an annual event but was canceled in 1917 and 1918 due to WWI, and in 1942-1945 due to WWII. 2011 is the 111th US Open.
The 1900 Olympics were the first modern Olympic Games to be open to women.
Fay Crocker, who was born in Montevideo, Uruguay was the first non-American born to win the U.S. Women's Open, winning the event in 1955.
Swimming
badminton
THE HEPTATHLON
ice hockey
because the water should not open our mouth
Is the Olympic fun center open
Three sports that I know of at one time allowed women to compete against men. Sailing at one time had several events open to men and women but in recent years has created separate events . Likewise shooting used to be open but they too have created separate events. Equestrian is the only current sport open to both sexes. Both shooting and equestrian have had women win gold medals competing against men. In the Winter Games the rules for luge allow for the doubles event to have women compete but I don't think this has happened as of yet.
1992 Games in Barcelona.
The silver medal winner in the Women's 10 Kilometer Open Water event at the Rio 2016 Olympics was Rachele Bruni.
Brazil won the bronze medal in the Women's 10 Kilometer Open Water event at the Rio 2016 Olympics.