In 1902 and 1904 he won the U.S. National Championships mixed doubles title together with Elisabeth Moore.

[3][4] In 1894, Grant first entered the singles at the U.S. Championships aged 14 years 8 months and is the youngest men's singles competitor in the tournament's history.

[6] In 1905 Grant and Edward Dewhurst made it to the final round of the lawn tennis doubles championship at the St. Nicholas Rink.

[7] Grant won the singles title at the U.S. National Indoor Tennis Championships, played on wooden courts at the Seventh Regiment Armory in New York, on five occasions (1903, 1904, 1906, 1908 and 1912).

[8] In 1914 Grant and George C. Shafer took the title from Gustave F. Touchard and William Cragin, in the championship round of the U. S. men's indoor doubles in New York City.