A 17-year-old Alaska girl on Tuesday became the first American woman to take a gold medal at the Tokyo Olympics. Lydia Jacoby won the women’s 100-meter breaststroke, topping 2016 champion Lilly King. South Africa’s Tatjana Schoenmaker won silver while King took bronze. “I was definitely racing for a medal. I knew I had it in me,” Jacoby told reporters. “I wasn’t really expecting a gold medal, so when I looked up and saw the scoreboard it was insane.” The race came down to the end. Jacoby’s time of one minute, 4.95 seconds was barely ahead of Schoenmaker’s one minute, 5.22 seconds. King finished in one minute, 5.54 seconds. “I’m so excited for Lydia,” King said. “I love to see the future of American breaststroke coming up like this and to have somebody to go at it head-to-head in the country. I definitely knew she was a threat and saw a …