He played five seasons of Major League Baseball as an outfielder for the New York Yankees, St. Louis Browns and Detroit Tigers.

[1] Mapes, who was listed with a height of 6 ft 3 in (1.91 m), and a weight of 205 lb (93 kg), was originally signed as an amateur free agent by the Cleveland Indians prior to the 1940 season.

After a season in the minors, Mapes was recalled to the Major League level, where he saw limited time as a backup to an outfield that contained Joe DiMaggio, Tommy Henrich, and Johnny Lindell.

[10] As Mapes' numbers started to decrease in 1951, including a batting average which fell to .216, the Yankees decided to cut ties with him.

In 1952, for the Tigers, Mapes hit a career-low .197, and was traded back to the Browns, with Neil Berry and cash, for Jake Crawford.