1967: Chicago is formed (as Chicago Transit Authority).
1968: The Beatles release "Sgt. Pepper's Lonely Hears Club Band."
1971: Earth, Wind, and Fire release their first album.
1974: Chicago, touring to promote "Chicago VII," includes a "Revolver"-indebted arrangement of "Got To Get You Into My Life" as an encore.
1978: Earth, Wind, and Fire receive a Grammy for their cover of "Got to Get You Into My Life," which the group also performed in the film flop "Sgt. Pepper's Lonely Hearts Club Band." Chicago mentions to reporters that they had hoped to be cast performing the song in the "Sgt. Pepper" film, rather than Earth, Wind, and Fire. At about the same time, Chicago split with their manager, James William Guercio, over "creative differences," leaving some to wonder if "Sgt. Pepper" was part of the reason.
2003: After many personnel changes for both groups, Chicago goes on tour with Earth, Wind, and Fire and the two groups release the concert DVD "Chicago/Earth, Wind & Fire Live at the Greek Theatre," which goes platinum. Earth, Wind, and Fire perform "Got To Get You Into My Life" on the DVD.
2009: Chicago and Earth, Wind, and Fire tour together again, including a June 18th performance in Portland at the Rose Quarter. No word on who will be awarded custody of "Got To Get You Into My Life."
Just for equity's sake, though, here's Chicago in 1979--meaning that guitarist/front man Terry Kath was already gone, replaced by Donnie Dacus--performing That Song:
(H/t to Grandmaster Keith.)