Madison Keys and Sloane Stephens have played just once before, in the second round of Miami in 2015. The unseeded Stephens upset Keys, the No.17 seed, 6-4, 6-2 and went on to reach the quarterfinals before losing to Simona Halep.
World No.83 Stephens is the lowest-ranked US Open finalist ever (aside from unranked Kim Clijsters in 2009). The only lower-ranked player to feature in any Open Era Slam final - again aside from the unranked - was No.111 Chris O'Neil, who won the 1978 Australian Open in a draw of just 32 players.
Both Madison Keys and Sloane Stephens had losing records this year coming into the North American hard court swing. Keys, who returned from her first wrist surgery in March, went 5-7 through Wimbledon, failing to reach any quarterfinal; Stephens, who returned from foot surgery at Wimbledon, was at 0-1 for the season.
Sloane Stephens had not scored a Top 20 victory at the US Open until this year - previously, her best win at Flushing Meadows had been No.24 Shahar Peer in the second round in 2011. En route to the final, she has tallied up three: No.10 Dominika Cibulkova in round two, No.17 Anastasija Sevastova in the quarterfinals and No.9 Venus Williams in the semifinals.
Madison Keys scored her first ever Top 10 win at the US Open with her defeat of No.4 Elina Svitolina in the fourth round; together with her victory over No.18 Elena Vesnina in the third round, her Top 20 tally here now stands at three.
The two finalists' previous major highlights have mirrored each other: in 2013, Stephens reached her maiden Slam semifinal at the Australian Open, and followed it up with a Wimbledon quarterfinal six months later. Two years later, Keys repeated both results. Stephens has also reached the fourth round on six further occasions at Slams to Keys's five more.
As a junior, Sloane Stephens' best Slam results were two semifinals - at Roland Garros in 2009 and the US Open in 2010, when she beat Elina Svitolina and Karolina Pliskova before losing to eventual champion Daria Gavrilova. Stephens was also a three-time girls' doubles Slam champion, triumphing at Roland Garros, Wimbledon and the US Open in 2010 alongside Timea Babos. Madison Keys' junior Slam record was just 4-4, and she never made a junior Slam quarterfinal.
As an unranked 14-year-old, Madison Keys made her WTA main draw debut in Ponte Vedra Beach in 2009 - and shocked World No.81 Alla Kudryavtseva 7-5, 6-4 in the first round before falling 6-3, 6-2 to Nadia Petrova. Two years later, she made her Slam debut at the US Open, beating Jill Craybas in the first round before losing to Lucie Safarova in three sets.
Sloane Stephens' WTA debut was at Indian Wells in 2010. Just days from her 17th birthday, the No.747-ranked wildcard into qualifying won two matches to make the main draw, beat Lucie Hradecka 7-6(5), 7-6(7) in the first round and stretched World No.14 Vera Zvonareva to a 6-4, 7-5 loss in the second round.
Sloane Stephens has never lost a final, owning a 4-0 record in championship matches. Three of her titles have been at International level, with her only Premier title coming at Charleston in 2016. Madison Keys has a 3-3 career record in Tour finals, with wins in Eastbourne in 2014, Birmingham in 2016 and Stanford this year - but all six of her finals have been at Premier level or above.
Last year, Madison Keys achieved her best streak of consistency yet by winning at least three matches in seven consecutive tournaments between May and September. Stephens' record for this feat is three straight tournaments - both at Strasbourg, Roland Garros and Eastbourne in 2015 and right now. Indeed, Stephens has won at least four matches in her last three events.
Should Madison Keys take the title, she will rise from her current No.16 to No.9 in the WTA rankings - her first time in the Top 10 since April, and two spots off her career high of No.7. If she loses, she will rise to No.12. Sloane Stephens, who set her career high of No.11 in 2013, has guaranteed a rise from No.83 to No.22 with a final, and would move to No.17 with a title.
Sloane Stephens has shared the playlist that's been soundtracking her summer resurgence with Natalie Gingerich Mackenzie for ESPN.com - it includes Justin Bieber, Lil' Mo and Nicki Minaj.
Gerald Marzorati has profiled Whitney Osuigwe, No.1 seed in the junior event, for the New Yorker.
Once again, there have been some spectacular shots hit on the WTA Tour in August. Remind yourself of some of the best.