First recorded by The Spencer Davis Group (US #10/UK #9/CAN #1 1967).
Other hit version by Chicago (US #49/UK #8/CAN #8 1971).
From the wiki: “‘I’m a Man’ was written by The Spencer Davis Group singer-songwriter Steve Winwood and record producer Jimmy Miller (not to be confused with the Bo Diddley song), and released as a single by The Spencer Davis Group in early 1967. It would be the last hit single by the band before the brothers Steve and Muff Winwood left the group to pursue solo careers.
“Chicago Transit Authority (now known as Chicago) recorded a cover version of ‘I’m a Man’ for their 1969 debut album, The Chicago Transit Authority. When the band’s popularity surged with the release of CTA’s second album, Chicago, in 1970, ‘I’m a Man’ was re-released as the B-side to a re-release of ‘Questions 67 and 68’ (also from the first album). Radio stations ended up playing both sides, and ‘I’m a Man’ peaked at #49 as a double-sided hit (the A-side peaked at #24) on the Billboard Hot 100 in 1971.”
Chicago Transit Authority, “I’m A Man” (1969):