Mezue ahịrịokwu na-esonụ: Horowitz bụ onye na-eduga na United States n'afọ ndị 1930 na 1940. Ọ bụ onye mmeri US Open na 1936, 1938, na 1943. N'afọ 1941, o meriri Samuel Reshevsky n'asọmpi U.S. Chess Championship (+0−3=13). O so n'Òtù Ndị Egwuregwu Chess nke United States mee egwuregwu Olimpik Chess ugboro anọ, na 1931, 1935,
1937, na 1950; nke mbụ n'ime ha atọ meriri site na U.S. N'egwuregwu egwuregwu egwuregwu redio ama ama nke United States na USSR na 1945, Horowitz meriri otu n'ime mmeri abụọ maka US site na imeri GM Salo Flohr. O kewara "obere egwuregwu" ya nke egwuregwu abụọ megide Flohr, na mbipụta 1946 nke otu ihe ahụ, kewara obere egwuregwu ya megide Isaac Boleslavsky.