Sezon 21
Bölümler
1 The Trials of J. Robert Oppenheimer 26 Oca 2009 
2 The Polio Crusade 2 Şub 2009 
3 The Assassination of Abraham Lincoln 9 Şub 2009 
4 A Class Apart 23 Şub 2009 
5 We Shall Remain (1): After the Mayflower 13 Nis 2009 
6 We Shall Remain (2): Tecumseh's Vision 20 Nis 2009 
7 We Shall Remain (3): Trail of Tears 27 Nis 2009 
8 We Shall Remain (4): Geronimo 4 May 2009 
9 We Shall Remain (5): Wounded Knee 11 May 2009