Mary Cain announced last week that she was turning professional.
American runners had a good showing last week in Moscow!
She wanted to race the 1500m as well, but a clerical error cost her a spot in that event.
The 27-year-old has set three PRs since June, including in the 3000m in London over the weekend.
Men's, women's 800m winners triumph in quick fashion on the final day of the USA Outdoor Track & Field Championships.