Wesley So and Alexander Onischuk qualified for a playoff to decide the open title.

UPDATE: Wesley So won the playoff and is the United States Champion. It is So’s four major tournament victory in the last nine months, following victories in the Sinquefield Cup, the London Classic and the Tata Steel tournament. So earns $50,000, while Alexander Onischuk won $35,000. 

In a final round steeped in drama, Sabina-Francesca Foisor captured the United States Women’s Championship on Sunday as she won and her closest rival, Nazi Paikidze, the defending champion, lost.

Foisor wound up with 8 points, Paikidze was clear second, with 7 points, while Irina Krush, a seven-time champion, settled for third, with 6.5 points.

Though the Women’s Championship was decided, the overall title had to wait until a playoff on Monday as Wesley So and Alexander Onischuk ended the regulation part of the tournament tied for first, each with 7 points. They were in a three-way tie with Varuzhan Akobian before the final round, but while So and Onischuk drew, Akobian lost to Hikaru Nakamura to end his chances for the title.

Nakamura and Fabiano Caruana, the defending champion, who also won his last round game, would up tied for third with Akobian, with 6.5 points apiece.

The two championships were at the Chess Club and Scholastic Center of Saint Louis. It is the ninth consecutive year that the club has hosted both events. The open tournament, a round-robin with 12 players, has a prize fund of $194,000. The women’s tournament, which is also a 12-player round-robin, has a prize fund of $100,000.

Foisor earned $25,000 for first place, while Paikidze took home $18,000, and Krush $13,000.

So, Onischuk and Akobian all had Black in the last round. Perhaps chastened by the fate of Nakamura and Caruana in Round 10, who both lost, So played it safe against Danial Naroditsky, a sophomore at Stanford University. So chose the solid Berlin Defense and Naroditsky, who apparently had two problem sets for college to finish after the game, was in no mood for a long fight either, so the game ended in a draw by repetition after 14 moves. It was a bit of a gamble by So to draw so quickly, but he was probably banking on the fact that winning with Black is very difficult and his co-leaders would likely also not be able to score more than a half point.

Short draws are common in the last round, and, indeed, Jeffrey Xiong and Yaroslav Zherebukh also drew soon after.

Onischuk had Black against Gata Kamsky, a five-time champion and former candidate for the World Championship. Considering Kamsky’s unstable play throughout the championship, is was conceivable that Onischuk might win. But Kamsky played a solid game and Onischuk did not feel the need to take much of a risk, so the game ended in an uneventful draw.

Akobian’s job against Nakamura was always going to be harder than Onischuk’s. But after the opening, Akobian seemed to be doing just fine. Then the pressure of the situation, combined with Nakamura’s precision, got to him:

Nakamura, Hikaru vs. Akobian, Varuzhan
ch-USA 2017 | Saint Louis USA | Round 11.2 | 09 Mar 2017 | ECO: A07 | 1-0
25. Rcb1 Bd6?!
25... h6 26. Qd1 Qxd1 27. Rxd1  )
26. Qd1! A hard situation for Akobian. He knew drawing the game was enough to tie for first, so entering an endgame which appears to be possible to draw was tempting.
26... Qxd1
26... Qxa2 27. Ra1  )
26... Qa7! Would still have been very comfortable for Black.  )
27. Rxd1 Be7 28. a4! Ra8 29. a5 Bd8 30. Ra1 The problem is that winning the White a-pawn removes defenses from Black's central pawns. There doesn't seem to be a way to protect them and attack the a-pawn.
30... Rda7 Delaying going after the a5 pawn doesn't help much.
30... Kf8 31. Ra4! Ke7 32. Bd2 Now Be3 is a threat, prevent Rda7. If Black cannot play that, he cannot successfully attack the a-pawn.
32... Rda7 33. Bxd5 Nxd5 34. Rxd5 Rxa5 35. Rdxa5 Rxa5 36. Rxc4  )
31. Bxd5 Nxd5 32. Rxd5 Bxa5 33. Bd2
33. Ra4 Is another way to win the black c-pawn, but Nakamura isn't in a hurry.  )
33... h6 34. Be3 Ra6 35. Ra3 Bc7 36. Rxa6 Rxa6 37. Rc5 Bd6 38. Rc8+ Kh7 39. Rxc4 Black has defensive chances, but clearly it will be a rather long defense. Nakamura wins it rather convincingly.
39... Be5 40. Rc8 Ra3 41. c4 Kg6 42. Kg2 h5 43. Re8 f6 44. Re7 Rc3 45. c5 Kh7 46. Kf1 Rc4 47. Ke2 Kg6 48. Kd3 Rc3+ 49. Ke4 h4 50. g4 Bh2 51. f4 Rc2 52. Kd3 Ra2 53. c6 Ra6 54. c7 Rc6 55. Kd4 f5 56. Kd5

In the only other decisive game of the day, Caruana played extremely provocatively with Black against Ray Robson, a student at nearby Webster University. It paid off after Ray spent too much of his time, and failed to take

Robson, Ray vs. Caruana, Fabiano
ch-USA 2017 | Saint Louis USA | Round 11.4 | 09 Mar 2017 | ECO: C11 | 0-1
12. Rb1 White's position appears fine, but Caruana now starts increasing the pressure on the queenside by playing provocatively.
12... a5 13. bxa5 Rxa5 14. Bd3 Ba6!? Going after the a3 pawn.
15. O-O Bxa3 16. Be3!? White had a nice option:
16. Bxa3 Rxa3 17. Qc1! Ra4 18. Nh5! And it is a real problem to deal with the threats to g7.  )
16... Be7
16... O-O 17. Bxh7+! Kxh7 18. Ng5+ Kg8 19. Qh5 And White would have a decisive attack.  )
16... g6 would stop Nh5 but
17. Ng5! And the threats of Nxf7 and Nxe6 are both troublesome.
17... Be7 18. Nxf7 Kxf7 19. Qf3 Ke8 20. Nxe6  )
17. Qd2? This is too slow. White misses the chance to create an immediate initiative. As a result, Black is essentially just a pawn up.
17. Nh5! Was the best try. Castling would allow White a lot of tactical options on the king side. And if Black continues:
17... g6 then White can keep the knight alive even on g7!
18. Ng7+ Kf8 19. Bh6 Kg8 20. Ne8 And it will next go to d6.  )
17... g6! Now White no longer has Nh5 and there isn't an easy way to create counterplay on the kingside to compensate for being down a pawn.
18. Rfc1 b4 19. h4 Ra3 20. Bxa6 Qxa6 21. Nh3 A typical maneuver. The idea is to play Bg5 to try to create dark-square weaknesses. But usually such a plan is launched when the position is completely closed and White has time to develop an attack. This is clearly not such a situation.
21... Na5 22. Bg5 White should have at least taken some measures to prevent Nb3, but Black would still have had a very nice position.
22... Nb3 23. Rxb3 Rxb3 24. Qe2 A cute little trick - but it is easy for Black to parry.
24... Qa8
24... Qxe2 25. Rc8+ Bd8 26. Rxd8#  )
25. Qb5 Rc3 And Black won quite easily.

Alexander Shabalov, a four-time champion, but the lowest seed in the field, had a horrid start to the event, scoring only half a point in his first five games. But he fought back in the latter stages, scoring fifty percent, and he almost secured his second win of the competition in the last round against Sam Shankland. Shabalov played a tricky move order on the White side of a Sicilian Defense to confuse Shankland and get him out of his comfort zone. It almost succeeded, but in the endgame Shabalov became too aggressive, costing him a possible victory:

Shabalov, Alexander vs. Shankland, Samuel L
ch-USA 2017 | Saint Louis USA | Round 11.6 | 09 Mar 2017 | ECO: B82 | 1/2-1/2
1. e4 c5 2. Nc3!? d6 3. f4 Aiming for a standard pawn structure in a closed Sicilian.
3... Nc6 4. Nf3 But White also keeps the option of playing d4 at some point. The idea behind this flexible move order is that it might make Black play a Sicilian line for which he is not prepared, as occurred in this game.
4... e6 5. d4 cxd4 6. Nxd4 Nf6 7. Be3 Shankland was probably planning to play a Najdorf Sicilian, but now he is in a Classical Sicilian. He clearly was not prepared for that as the subsequent course of the game demonstrates.
7... Be7 8. Qf3 e5?! 9. Nf5 Bxf5 10. exf5 O-O 11. O-O-O Qa5 12. Bc4 Rac8 13. Bb3 White seems to have an ideal set-up.
13... exf4 14. Qxf4 Rfe8 15. Kb1 Bd8 16. g4 Qe5 g5...g6 would have been very strong for White. Now Black manages to exchange queens, but it becomes hard to keep the material balance after:
17. Qxe5 Rxe5
17... dxe5 18. g5 Ng4 19. g6  )
17... Nxe5 18. Bxa7 Nfxg4 19. Nb5  )
18. Bf4 Ra5 19. h3 Bc7 20. Bxd6 Bxd6 21. Rxd6 White is up a pawn and Black has no compensation for his material deficit.
21... Kf8 22. Rhd1 h6 23. a3 Re5 24. R6d3 Rce8 25. Nd5 There was no need for White to try to force exchanges.
25. Ba4  )
25... Ne4 26. Nc7 White is playing more aggressively in the endgame than was needed.
26... Rc8 27. Rd7 Re7 28. Nb5 a6 29. Rxe7 Nxe7 30. Rd4 Nf2 31. Nc3 Nxh3 32. Rd7 Nf2 33. Nd5 Nc6 34. Nb6
34. Ne3! Would keep the g-pawn defended.
34... Ne5 35. Rxb7  )
34... Ne5! 35. Rxb7 Rd8 36. c4 Ne4 37. Rc7 Rb8 38. c5 Nxc5 39. Rxc5 Rxb6 40. Rxe5 Rxb3 41. Ra5 Rb6 42. Re5

For Shankland, it was a forgettable championship as he failed to do too well against the lower-rated opponents.

In the women’s section, all eyes were on the top two matches. Paikidze was playing White against Jennifer Yu, while Foisor had Black against Apurva Virkud, so Paikidze appeared to be the slight  favorite before the round began. But while Paikidze played for a slight edge throughout the game, Foisor had the initiative almost from the start. After the opening, it was clear that Virkud had little chance. Foisor ended the game with fireworks:

Virkud, Apurva vs. Foisor, Sabina-Francesca
ch-USA w 2017 | Saint Louis USA | Round 11.2 | 09 Apr 2017 | ECO: E32 | 0-1
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 O-O 5. Nf3 c5 6. dxc5 Na6 7. c6 bxc6 8. g3 d5 9. Bd2 d4 10. Ne4 Rb8 11. Nxf6+ Qxf6 12. Bg2 e5 13. O-O Bf5 14. Qc1 Bxd2 15. Qxd2 h6 16. Qa5 c5 17. b3 e4 18. Nd2 Rfe8 19. Rad1 Rb6 20. Nb1 Qe7 21. e3 Bg4 22. Rd2 Nb4! 23. exd4
23. a3 Nc6 Would force the queen to a4 a pretty ugly place her. Clearly this position isn't any fun for White.  )
23... e3! 24. fxe3 Qxe3+ 25. Kh1 Rf6! The most precise! Sabina unleashes a lethal kingside attack.
26. Rg1 Qxg1+! Black had many nice ways to win - but this the prettiest.
27. Kxg1 Re1+ 28. Bf1 Rfxf1+ 29. Kg2 Rg1+ 30. Kf2 Ref1+
30... Rxb1 Was winning, too, but Black has a forced mate instead.  )
31. Ke3 Rf3+
31... Rf3+ 32. Ke4 Re1+ 33. Re2 Rxe2#  )

This clearly put a lot more pressure on Paikidze. She started to play more provocatively, while Yu kept calm and precisely exploited all of Paikidze’s inaccuracies. Eventually, it took its toll on Paikidze’s position:

Paikidze, Nazi vs. Yu, Jennifer R
ch-USA w 2017 | Saint Louis USA | Round 11.1 | 09 Apr 2017 | ECO: D11 | 0-1
27. Bf1 Qa4! 28. Nc3 A nice way to generate threats on the queenside.
28... Qa5 Black has a threat now: Bb4, after which the White queenside could fall apart.
29. a3 Bb3 30. Rc1 Rd8 31. Qe2 Bc5 32. Bd2?! Paikidze continued to play too ambitiously.
32... Bc4! 33. Qe1
33. Qxc4 Rxd2 And the pawn on f2 would fall.  )
33... Bxf1 34. Kxf1 Qa6+ 35. Kg2 Qd3 The Black queen has found a powerful post. By now, Foisor had already won her game and Paikidze was clearly disappointed in her position. She did not manage to put up the best resistance the rest of the way.
36. Rd1 Qc2 37. b4 Bf8 38. Nd5 Nd6 39. Bc1 Rc8 40. Kg1 Qxe4 41. Qf1 Nf5 42. Be3 Rc6 43. Qd3 Qxd3 44. Rxd3 Rd6 45. b5 Nd4 46. Nb4 Nxb5 47. a4 Rxd3 48. Nxd3 Nc3 49. Nxe5 Nxa4 50. Nc6 a5 51. Ne5 Bc5

Foisor was sitting awaiting the result of Paikidze’s game. When it became clear that she had won, Foisor, who is originally from Rumania and whose mother, Cristina Adela Foisor, a Rumanian national champion, died in January, broke down in an emotional embrace with her fiancé, Elshan Moradiabadi, a grandmaster originally from Iran. There is a video of the moment on the site of the United States Chess Federation.

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Parimarjan Negi is an Indian grandmaster who is the second-youngest ever to earn the title (at 13 years 4 months and 22 days). Ranked No. 80 in the world, he is a junior at Stanford University. He can be found on Twitter at @parimarjan.