Kathryn Erbe's pregnancy was incorporated into the show by having her character Alexandra, be a surrogate mother.
The show is filmed in Chicago. The actors/actresses trained for 3 months beforehand with retired S.W.A.T. personnel and real Chicago Police officers.
Julianna Margulies wore a wig for her character Alicia
Eli Gold, played by Alan Cumming, is modeled after Chicago politician Rahm Emanuel, former chief of staff of president Barack Obama.
While all the fly-over shots, skylines and cityscapes really are of Miami, Florida, any beach scenes during the series, were filmed at Manhattan Beach, a suburb of Los Angeles.