Showalter won U.S. Championship matches against Max Judd (1891/92, +7−4=3), Albert Hodges (1894, +7−6=4), S. Lipschütz (1895, +7−4=3), Emil Kemény (1896, +7−4=4), and John Finan Barry (1896, +7−2=4).
He lost championship matches to Max Judd (1890, +3−7=0), S. Lipschütz (1892, +1−7=7), Albert Hodges (1894, +3−5=1), Harry Nelson Pillsbury (twice, 1897 (+8−10=3) and 1898 (+3−7=2), and Frank Marshall (1909, +2−7=3).
Pollock (1891, +3−2=3), Emanuel Lasker (1892/93, +2−6=2), Jacob Halpern (1893, +5−3=1), Adolf Albin (1894, +10−7=8), Dawid Janowski (four times: 1898, +2−7=4; 1899, +4−2=0 and +4−2=1; 1916, +2−7=2), Borislav Kostic (1915, +2−7=5), and Norman T. Whitaker (twice: 1916, +6−1=0 and 1918, +1−4=3).
Showalter was known as "the Kentucky Lion" after his birthplace and his hairstyle, which consisted of a thick mane down the back of his neck, and perhaps also his playing strength.
The content of the induction speech was supplied by Kevin Marchese of Columbus, Ohio, who is currently writing a biography on Showalter that was slated to be delivered in late 2016.