Rio de Janeiro — Allyson Felix and LaShawn Merritt are two savvy track stars who've been around long enough to know that not everything always goes to plan.

Over the final, topsy turvy 30 minutes of running at the Olympic track on Saturday night, both Americans came away with prizes they'd been wishing for all along.

Those prizes were both gold, and the United States exited the final night of action at Olympic Stadium with 31 medals — the most it has taken in a non-boycotted Olympics since 1956, when the world and track were both very different places.

One of those 31 had been looking to go to 41-year-old Bernard Lagat in the 5,000 meters. He actually finished fifth but two runners ahead of him, including American Paul Chelimo, were disqualified for interference. A review ensued, Chelimo was reinstated to silver and Lagat dropped to fourth — a bummer for the elder statesman of the U.S. track team, but some sort of sign for the team as a whole: Even when it lost, it won.

And the biggest surprise came in the men's 1,500 meters, where Matt Centrowitz shocked the field in a slow race and became the first American to win a gold in the "metric mile" since the 1908 Olympics.

Felix's win was much more clear-cut. She now has six gold medals, improving her all-time record for women in Olympic track and field.

This has been an adjust-on-the-fly year for America's best-known track star — her failure to make the team for the 200 meters, her jaw-dropping silver-medal moment when a diving Jamaican beat her in the 400 and more. But on back-to-back nights, she took relay gold.

This time, she ran a 49.66-second anchor lap in the 4x400. Over the second and third laps, Americans Natasha Hastings and Phyllis Francis held big leads, only to watch them dwindle dramatically as they legged out their final meters. Felix took the green baton about two steps ahead of Jamaica's Novelene Williams-Mills, and slowly, steadily expanded it for a total time of 3 minutes, 19.06 seconds and a 1.28-second win. Yes, the United States may have relay problems — see, the men's 4x100, which flamed out again the night before — but this certainly isn't one of them. This race has gone to America six straight times.

The look on Felix's face as she crossed the line and waved the baton said what words could not: Thank goodness, it's finally over.

Merritt looked equally relieved. He was caught in the tail wind of South African Wayde van Nierkerk's world-record 400 run earlier in the week and settled for bronze. Then, Merritt was a bit player in the Usain Bolt going-away party, finishing in fifth the 200.

But Bolt was long gone — having stopped by the track quickly to receive gold medal No. 9 and take a selfie with 5,000-meter winner Mo Farah — and South Africa had left the building, too.

As Felix had done minutes earlier, Merritt took a narrow lead and opened it way up. This relay gold goes with those he took in both the relay and the 400 flat in 2008.

It wasn't all perfect for the red, white and blue.

High jumpers Chaunte Lowe, a mother of three who finally felt ready for her Olympic moment, and Vashti Cunningham, daughter of former NFL quarterback Randall, finished fourth and 13th in a contest taken by Ruth Beitia of Spain.

But on this night, every unexpected setback for the U.S. had its own offsetting surprise, especially for underdogs like Chelimo and Centrowitz.

Centrowitz was considered a contender in the 1,500 — and in this case, contending meant winning a race in a leisurely pace of 3 minutes, 50 seconds for a .11 margin over Taoufik Makhloufi of Algeria.

"Doing my victory lap, I literally kept screaming to everyone I know, 'Are you kidding me?'" Centrowitz said.

But like everything else red-white-and-blue on this night, the Americans were no joke.