Leon Rosen was an American chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

 master.

Born in Warsaw, Poland (then Russian Empire

Russian Empire

The Russian Empire was a state that existed from 1721 until the Russian Revolution of 1917. It was the successor to the Tsardom of Russia and the predecessor of the Soviet Union...

), he left for Paris, France, and next emigrated to the United States. He took 4th at Paris 1896 (Dawid Janowski

Dawid Janowski

Dawid Markelowicz Janowski was a leading Polish chess master and subsequent French citizen....

 won), and took 14th in the Paris 1900 chess tournament

Paris 1900 chess tournament

The Paris 1900 chess tournament was an event held in conjunction with the Exposition Universelle , one of the world's most notable fairs or exhibitions held during the second half of the nineteenth century and designated a "World Exposition" by the Bureau of International Expositions...

 (Emanuel Lasker

Emanuel Lasker

Emanuel Lasker was a German chess player, mathematician, and philosopher who was World Chess Champion for 27 years...

 won). In that time, he appeared on the New York 1900 Census. He took 18th at Excelsior 1905 (U.S. Open Chess Championship

U.S. Open Chess Championship

The U.S. Open Championship is an open national chess championship that has been held in the United States annually since 1900.-History:Through 1938, the tournaments were organized by the Western Chess Association and its successor, the American Chess Federation .The United States Chess Federation ...

, Edward F. Schrader won), took 2nd, after Julius Finn

Julius Finn

Julius Finn was an American chess master.Born into a Jewish family in Władysławowo, Poland , he came to New York in 1887. From a humble start as a street peddler on the Lower East Side, Finn swiftly rose to become New York’s champion chess master and one of the country’s best blindfold chess...

, in the 1907 New York State championship, took 2nd, behind Clarence S. Howell, at Trenton Falls 1908 (Quadrangular). In 1909, he shared 1st with Manuel Ayala and Otto Roething in the Manhattan CC championship. In January 1910, Rosen, the Parisian expert, beat José Raúl Capablanca

José Raúl Capablanca

José Raúl Capablanca y Graupera was a Cuban chess player who was world chess champion from 1921 to 1927. One of the greatest players of all time, he was renowned for his exceptional endgame skill and speed of play...

 (third round), Jacob Rosenthal

Jacob Rosenthal

Jacob Carl Rosenthal was an American chess master.Born in Bialystok, Poland , he became a citizen of the Netherlands. Finally, he emigrated to the United States. He lived and participated in several local chess matches in New York City Jacob Carl Rosenthal (12 October 1881, Bialystok – 23 October...

(semi-final), and J. Marder (final), and won in the Rice Chess Club tournament in New York.

Rosen played in several matches in New York; Manhattan CC vs. Franklin CC (1909), Rice CC vs. Brooklyn CC (1909), Brooklyn CC vs. Rice CC (1909), Manhattan CC vs. Franklin CC (1910, 1911, 1912). He participated in American Chess Bulletin tournament in 1914/15, and in the 1923 New York Metropolitan team tournament.