An open national chess championship that has been held in the United States in different cities annually since 1900 consecutively without any single year interruption until the 120th edition in 2019, which makes it the longest running annual chess tournament in the world! Then there was no contest held in 2020 due to Corona Pandemic as in almost all series, since the 121st edtion in 2021, the U.S. Open takes place annually again.

Note: The U.S. Open Chess Championship (commonly known as U.S. Open) is not to confuse with the U.S. (Invational) Chess Championship.

Record winner of the U.S. Open is Pal Benko (8x), followed by Reuben Fine (7x).

Bobby Fischer won it 1957 as a teenager in Cleveland (on tie-break above Arthur Bisguier). First winner in 1900 (the first Western Chess Association Championship) at Excelsior, Minnesota was american chess master Louis Uedemann.

Non-US winners are rather rare: Boris Kostic, Carlos Torre Repetto, Arturo Pomar Salamanca, Daniel Yanofsky, Bent Larsen, Vlastimil Hort, Florin Gheorghiu, Boris Spassky, Viktor Korchnoi, Vladimir Akopian, Smbat Lputian, Eduardas Rozentalis, Evgeniy Najer, Vadim Milov, or Judit Polgar (plus prominent émigrés such as Edward Lasker, Nicolas Rossolimo, Anatoly Lein, Leonid Shamkovich, Roman Dzindzichashvili, Lev Alburt, Boris Gulko or Dmitry Gurevich).

Through 1938, the tournaments were organized by the Western Chess Association (originally the Northwestern Chess Association) and its successor, the American Chess Federation (1934–1938). The United States Chess Federation (USCF) has run the tournament since 1939.

In the early years of the tournament, the number of entrants was small, the U.S. Open was a round robins event among whoever happened to show up! Play was conducted as with Preliminaries, Championship Finals, and Consolation Finals. It remained a round robin through a semi-invitational phase, but gradually introduced preliminary and final sections to accomodate more players.

An important innovation came in 1946 at Pittsburgh, as the Swiss System, advocated by Kenneth Harkness, was used for the first time to determine placement from the preliminary to the various final sections.

Starting in 1947, the Swiss system under the guidance of George Koltanwski took over the whole shebag, and subsequently the U.S. Open Chess Championship has been played always as an Open to accommodate a large number of players. Through some years, the tournament had 12 or 13 rounds and lasted nearly two weeks, this caused to be too expensive for many players, thus it is played today as most other Chess Open in 9 rounds in 9 days.

Tournament participation grew through the 1950s and 1960s. Milwaukee 1953 had 181 entrants, setting a new record for the tournament. Cleveland 1957 had 184 players, and San Francisco 1961 set another attendance record with 198 players. The 1963 Open at Chicago had 266 entries, making it the largest chess tournament held in the United States to that time.

Pasadena 1983's official count was 836 players, due to tthe participation of Viktor Korchnoi, it is still the best turnout in the history of the U.S. Open.

In the 2000s, the fields were over 400 to 500 entries, sometimes fringing a bit with many winners involved in one of those huge ties for first since the 1990's.

The cash prizes awarded were large for their time and added to the tournament's popularity, eg. in 1962, the entry fee was $20, with a first prize of $1000, second prize $500, third $300, fourth $200, fifth $100, sixth through tenth $50 and eleventh through fifteenth $25. Additional cash prizes were awarded to the top women, the top junior, and for the best scores in the Expert A, B, and C classes. The 2016 guaranteed prize fund was $40,000, with $8000 for first place.

In the 1983 U.S. Open in Pasadena, California, back when the US Open tournament was a 12 rounds, Viktor Korchnoi faced in the last six rounds of the event a bunch of the best players America then had to offer, winning the Open together with Larry Christiansen (Korchnoi first on tie-break at his first and only entry):

Watch out new analysis from Korchnoi's games, by Dennis Monokroussos:
http://worldchess.com/2016/06/10/korchnoi-at-the-u.s.-open/ (World Chess)

Sources: Wikipedia, Chessgames, USCF (The United States Chess Federation)

http://en.wikipedia.org/wiki/U.S._Open_Chess_Championship (Wikipedia)
http://www.uschess.org/tournaments/2014/usopen (Tournament Homepage)
http://www.chessgames.com/perl/chesscollection?cid=1021229
(U.S. Open 1983, selected games)
http://www.chessgames.com/perl/chesscollection?cid=1021137
(U.S. Open Index Collection 1900-2014, selected games)

Grandmaster Larry Christiansen in 2007, photo courtesy of Pittsburgh Chess Club

Christiansen, Larry Mark (born June 27, 1956)

American Grandmaster (1977). Great attacking player. Chess coach and author.

U.S. Champion in 1980, 1983, and 2002. He has represented the United States nine times at the Chess Olympiad and three times as (non-playing) Captain: Christiansen played on the United States Olympiad teams of 1980, 1982, 1984, 1986, 1988, 1990, 1992, 1996 and 2002.

He won twice the prestigious Linares tournament, once as clear first, once tying with Karpov.

Christiansen showed exceptional strength at an early age. In 1971, he became the first junior high school student to win the National High School Championship. He went on to win three invitational U.S. Junior Championships in 1973, 1974, and 1975.

In 1977, at age 21, Christiansen became a Grandmaster without first having been an International Master, an accomplishment shared by only a handful of others.

Silver medal at the World Junior 1975 (Vice World Junior Champion).

Won Torremolinos, Costa del Sol (17^th) 1977, Linares (2^nd) 1979 (ahead of Viktor Korchnoi), World Open in Philadelphia, Pennsylvania 1980 (joint), U.S. Open in Palo Alto, California (82^th) 1981 (five players sharing first place), Linares (3^rd) 1981 (together with Anatoly Karpov, ahead of Larsen, Ribli, Spassky, Kavalek, Portisch, Ljubojevic, Gligoric, Quinteros, and two Spain players), U.S. Open in Pasadena, California (84^th) 1983 (together with Viktor Korchnoi, the winner on tie-break score, who had agreed spontaneously to participate in the U.S. Open after his scheduled Candidate match versus Garry Kasparov at Pasadena could not be held, more than 800 players coming in, including the best players America then had to offer), New York Open 1985 (six players sharing first place), U.S. Open in Somerset, New Jersey (87^th) 1986 (outright), Doeberl Cup, Canberra (26^th) 1998, Cologne - Porz GM 1988, World Open in Philadelphia, Pennsylvania 1989 (jointly), Long Beach Open 1989, Munich, SKA-Mephisto (4^th) 1991 (clear first, 1.5 points ahead of Gelfand, Beliavsky, Hübner, Hertneck, Nunn, Anand, Judit Polgar, Hort, Lobron, Yudasin, Zsuzsa Polgar, Wahls, and Kindermann; second and final GM norm for Gerald Hertneck), Vienna GM 1991 (again with 1.5 points leading, ahead of Epishin, Nunn, Ribli, Judit Polgar, Mokry, and four Austrian players), Nettetal GM 1994 (ahead of Lobron, Lau, young Leko, veteran Taimanov, amongst others), Wiesbaden Open 1994, Eupen CERA Rapid Open 1997, Reykjavik Open (18th) 1998 (outright), Merida (Carlos Torre Repetto Memorial, Open) (11^th) 1998, Essen (1^st Julian Borowski GM) 1999 (shared with Vadim Zvjaginsev, Emil Sutovsky, and Rustem Dautov who was first on tie-break score), Canadian Open Chess Championship in Sackville (38^th) 2001 (together with Tony Miles), Curacao Open 2008 (first on tie-break), Bermuda Open 2011 (first after play-off match over Pascal Charbonneau).

Second shared at Lone Pine, California, Louis D. Statham Tournament (6^th) 1976 (former World Champion Petrosian won the Open; Christiansen finished best second on tie-break, alongside with Smyslov, Panno, Najdorf, Quinteros, Miles, Rogoff, Browne, and Forintos).

In matches he beat Reshevsky 4.5-3.5 in 1984, and Kavalek 2.5-0.5 in 1987, amongst others.

Trivia: U.S. Championship, Semi-Finals: Christiansen vs. Seirawan 8-6 (after speed play-off on Saturday 6th September 1997)
<< After their semi-final match ended deadlocked at 2-2 with a draw (classical chess) today, Yasser Seirawan and Larry Christiansen embarked on a marathon series of mini-matches: The G/25 match was tied, each player winning with White.
The same occurred in the G/15 match. No less than 4 G/5 matches were necessary before Christiansen finally overwhelmed Seirawan's Kalashnikov Sicilian. The two players played *11* total games today, not a one being drawn. >>
http://theweekinchess.com/html/twic148.html#2%29 (A fatigued Christiansen then lost the final to Benjamin)

Frequent and successful player at the Bundesliga, Germany. Best ELO rating 2625 in July 1992, with peak ranking as no. 21= of the world in that same ELO list II / 1992 (July to December), being already no. 23= in January 1982, and no. 24= in January 1987.

Christiansen describes his playing style as "aggressive-tactical" and he lists his favorite opening as the Sämisch King's Indian. Christiansen is also renowned for his quick wit and humor, as well as his enthusiasm for teaching students. He is also one of the most prolific internet chess players, having played tens of thousands of games online on ICC (Internet Chess Club).

He is the author of popular chess books, ie.: Dutch Defense (1979). Storming the Barricades (2000) and Rocking the Ramparts (2004). Inducted into U.S. Chess Hall of Fame in 2008.

Larry Christiansen is married to Natasha Christiansen (*1962), a lawyer and Woman Candidate Master (WCM).

Sources:

CNC: http://www.chessnc.com/biography/person-473.html
Chessgames: http://www.chessgames.com/perl/chessgame?gid=1069116
Wikipedia: https://en.wikipedia.org/wiki/Larry_Christiansen
U.S. Chess Champs: http://www.uschesschamps.com/bio/larry-christiansen

Portrait (in Spanish language by Javier Cordero Fernández):
http://www.ajedrezdeataque.com/04%20Articulos/38%20Varios4/Christiansen/Christiansen.htm 

Palmarès (in Spanish language):
http://www.ajedrezdeataque.com/04%20Articulos/38%20Varios4/Christiansen/Palmares.htm

Larry’s legendary 12 moves miniature: 
http://www.chessgames.com/perl/chessgame?gid=1069116
Christiansen beating Anatoly Karpov within 12 moves in classical chess after the latter blundered.

One of his best games, vs. Spassky: http://www.chessgames.com/perl/chessgame?gid=1088727

Korchnoi vs. Christiansen, U.S. Open at Pasadena in 1983:
http://www.chessgames.com/perl/chessgame?gid=1082768