The billboards went up over Interstate 5 in Downey, Calif., which is slightly southeast of the stadium, and encouraged the Southern California native to sign with the Clippers.
One of the images contains a personalized California license plate that reads "KAWHI," with the hashtag "#ClipperNation." The other billboard reads "King of SoCal," with the hashtag "#KAWHI2LAC."
League sources told ESPN on Monday that the Clippers knew nothing about the billboards. Clippers head coach Doc Rivers previously was fined $50,000 for tampering after the coach made comments about Leonard, comparing the forward to Chicago Bulls icon Michael Jordan.
Leonard, 27, can become a free agent this off-season after guiding the Raptors to their first NBA championship. League sources told Yahoo Sports on Sunday that Leonard is expected to decline his 2019-20 player option to become an unrestricted free agent this summer.
NBA teams can begin negotiating with free agents next Sunday. No contracts can be signed until July 6.