Keri Russell as Elizabeth Jennings in “The Americans” pilot. (Craig Blankenhorn/FX)

FX has picked up ”The Americans” for a 13-episode second season.

The pickup comes four episodes into the first season of the drama, which stars Keri Russell and Matthew Rhys as married KGB spies posing as American travel agents in suburban Washington during the Reagan years.

The show’s unveiling, which averaged 5.1 million viewers, was the most watched FX series debut in the network’s history.