Called up for his first major league start at age 21, Harper halted the National League-record 24-game losing streak of the 1899 Cleveland Spiders by winning 5-4. When the NL was cut from twelve teams to eight in 1900, he was transferred to the Cardinals, for whom he went 23-13 in 1901, finishing second in the NL in wins and winning percentage. After two more average years, he again won 23 (losing 9) with a career-low 2.37 ERA for the Reds and was third in the NL in wins and winning percentage. After missing most of 1906 with a finger injury and bone chips in his elbow, he was traded to the Cubs in October. A holdout the following year ended his major league career.