TOKYO, Aug 3 (Reuters) - Athing Mu of the United States won the gold medal in the Olympic women"s 800 metres final on Tuesday, her country"s first victory in the event in more than half a century, as her compatriot Raevyn Rogers grabbed bronze. The absence of South Africa"s double champion Caster Semenya, ruled ineligible due to heightened testosterone levels, opened up the field to a new winner and the 19-year-old Mu took full advantage. She dominated the race, leading almost from the start and crossing the line clear of her rivals in a time of 1:55.21, to secure the U.S. a second gold in the event after Madeline Manning"s triumph in 1968. Keely Hodgkinson of Britain took silver. Mu, whose parents moved to the U.S. from Sudan two decades ago, said it was "awesome" that she won gold at such a young age. "I wasn"t really putting gold on that, but as it got closer to the final today, I was like, "Yeah, we want gold"," the 19-year old said. Mu said getting ahead quickly was part of her strategy. "I wanted to go early from the front and not let anyone mess up my race plan. I just wanted to do my own thing," she said. Mu"s time was an American national record. "I knew it was pretty close but to do that again feels amazing," she said. Along with the bronze for Rogers, who posted a personal best of 1:56.81, the pair became the first U.S. medallists in the event since 1988. Britain"s Hodgkinson ran a brilliant second half of the race to earn silver and after the race, she was excited about two teenagers winning medals at the grandest stage. "There"s not just one 19-year old in the race, there is two...which is unbelievable. Hopefully it stems for a good competitive 10-15 years ahead and faster times on the horizon," she said. The 19-year old broke 2004 Olympic champion Kelly Holmes"s British national record with a time of 1:55.88. "Kelly is a massive legend of the sport and she always will be with that double Olympic gold. She sent us all a few messages the last couple of day," she told reporters. "I am quite in shock about that time." Asked how she would celebrate, Hodgkinson said; "You"ll catch me in the pub. One guilt-free night out before I finish the rest of the season and then off-season in September." Rogers, 24, said it felt "surreal" to win bronze. "I think it"s settling in. Just being able to take something back home, I"m really proud," she said. Rogers dedicated the medal to her mother who is celebrating her birthday today. "It"s morning time in America, so she"s going to have this whole day to celebrate. I"m just really happy. I just want to make them proud," she said.