She finished with a time of 1.10.10, just .08 seconds behind winner Natalie du Toit of South Africa. Stone took silver in the event at the 2008 Paralympics in Beijing.
The 22-year-old is expected to compete in at least five more events through September 7. Ahead of her are the 100 backstroke, 4×100 freestyle relay, 400 freestyle, 50 freestyle, 100 freestyle. Members of the 4×100 medley relay have not been decided.
This is the third Paralympics for Stone. She first competed at age 15 in Athens, Greece.
Stone has lived at the Olympic Training Center in Colorado Springs for the last two years.
Her mother, Linda, adopted Stone when she was four years old and living in a Romanian orphanage.
Stone’s leg was amputated above the knee after four previous surgeries failed to correct a medical condition known as PFFD (Proximal Femoral Focal Deficiency).