Six-time Olympic champion Allyson Felix qualified for her fifth Games with a second-place finish in the 400m at the US trials.
The 35-year-old, who has nine Olympic medals in total, clocked 50.02 seconds behind winner Quanera Hayes.
Tokyo will be Felix's first Olympics as a mother, having welcomed daughter Camryn in 2018.
"It has been a fight to get here and one thing I know how to do is fight," said 13-time world champion Felix.
"To make the fifth one - so special."
Felix returned to the track two years ago following life-threatening complications arising from the birth of her daughter - Camryn spent the first month of her life in intensive care.
"Man, it has been a fight to get here and one thing I know how to do is fight, and I just did that all the way home," Felix said.
She added: "Society tells us a lot of times that if you have a child [then] your best moments are behind you.
"But that's absolutely not the case. I am representation of that."
Elsewhere at the trials in Eugene, Oregon, Trayvon Bromell continued his stellar year by winning the men's 100m and booking his ticket to Tokyo.
The 25-year-old, who holds the world-leading time of 9.77secs, ran 9.80secs, with Ronnie Baker second and Fred Kerley third, both in personal best times.
Justin Gatlin, hoping to reach his fourth Olympics, finished last.
Tokyo will be Bromell's second Olympics, having finished eighth in the 100m in Rio before suffering a career-threatening Achilles injury in the 4x100m final.
"It's a marvellous feeling," he said.
Rio 2016 Olympian Rudy Winkler threw a new American record of 82.71m to win the hammer throw, while Keturah Orji also reached her second Olympics with a meeting record of 14.52m in the women's triple jump.