LaShawn Merritt anchored the US 4x400-meter relay team to win an Olympic gold medal and regain control of the event at the games.
It's the ninth total medal, and sixth gold (five in relays), for Felix, the most decorated USA female track and field Olympian and tied with Merlene Ottey for most overall.
"It's very special. It was great to join these women tonight".
The toughest, without a doubt, Felix said of her 2016.
After initially not qualifying for the race, the US was granted a re-run when officials ruled that Felix had dropped the baton because she was bumped by another runner.
The Americans appealed successfully, arguing that Felix had been impeded by a Brazilian runner, and went through at China's expense after being allowed to race by themselves in a solo heat in the evening. Jamaica's Elaine Thompson, running the second leg after Christania Williams before handing over to Veronica Campbell-Brown and Shelly-Ann Fraser-Pryce, narrowly missed out on a Usain Bolt-style sprint treble after her victories in the 100m and 200m.
"Wonderful experience. My first Olympics".
McQuay was the only holdover from the US 4x400m team that won the silver medal at the 2012 Olympics. The USA and Jamaica also finished gold-silver in London.
"People are at home watching - watching 2012, watching 2008", said Felix, 30, who wrapped up her fourth Olympics and now has nine total medals.