Half the pilot (the interiors) was shot in Toronto, while the exterior scenes were shot on location in New York.
Marlene Lawston, who played Nicky Reagan-Boyle in the pilot, was replaced by Sami Gayle beginning in Episode 4, Officer Down (2010). Marlene is most well-known for starring as Julia in the movie Flightplan (2005) with Jodie Foster. Marlene's final acting role was in the pilot of Blue Bloods.
The scene where Danny obtains information on the kidnapped little girl by sticking the suspect's head in the toilet was recycled from the 2006 episode Thinking Makes It So (2006). Dennis Farina of Law & Order who played NYPD Detective Joe Fontana used the same method to locate a kidnapped little girl.
The actual NYPD Police Commissioner during the first four seasons of the series was two time appointee Commissioner Raymond Walter Kelly. In 2014, during the show's fifth season, Commissioner William Bratton assumed office. Henry Reagan's tenure of office, stated to have been sometime in the 1970s, would most likely have occurred during the tenure of Commissioner Patrick V. Murphy.