One of the people that is documented in the series is Michael Romanoff who owned a successful restaurant in California. People believed he was a Romanov, but he was really a con man and had no connection to the family.
Weiner worked with John Slattery, Cara Buono, Christina Hendricks and Jay R. Ferguson in the past on Mad Men.
Corey Stoll (Michael Romanoff) and Andrew Rannells (David Patton) both starred as love interests in Girls (2012).
While not attributed, filming was also conducted in Ontario, Canada. Obvious Dollarama (Canadian company) as well as other retail signage is displayed and so Whitby and Toronto were ignored in listing if filming locations.
Jon Hamm was offered a role but he declined it.