Texas A&M's Jermaisha Arnold and Michigan's Ziyah Holman earned the top two spots for the United States in the women's 400-meter final at the North American, Central American and Caribbean Athletic Association (NACAC) Under-23 Championships at the National Stadium in San Jose, Costa Rica. Arnold produced a meet-record 50.68 seconds to capture gold, eclipsing the 2016 mark of 51.02 achieved by Jamaica's Chrisann Gordon. Holman also ran faster than the previous record by securing silver in 50.95.