Until Thursday, in the women’s 400, only two women had gone under 48 seconds, both from the 1980s — Marita Koch of East Germany and Jarmila Kratochvilová of what was then Czechoslovakia. Koch went 47.60 in 1985. Two years earlier, at the 1983 worlds in Helsinki, Kratochvilová went 47.99.

Until Thursday, that was the championship record.

Sydney McLaughlin-Levrone crossed in 47.78.

Marileidy Paulino of the Dominican Republic, the Paris 2024 Olympic and 2023 worlds champion, finished in 47.98 — one-hundredth faster than Kratochvilová. But good enough only for second.