Season 23
Episodes
1 God in America (Parts 1–2) Oct 11, 2010 
2 God in America (Parts 3-4) Oct 12, 2010 
3 God in America (Parts 5-6) Oct 13, 2010 
4 Robert E. Lee Jan 3, 2011 
5 Dinosaur Wars Jan 17, 2011 
6 Panama Canal Jan 24, 2011 
7 The Greely Expedition Jan 31, 2011 
8 Triangle Fire Feb 28, 2011 
9 The Great Famine Apr 11, 2011 
10 Stonewall Uprising Apr 25, 2011 
11 Soundtrack for a Revolution May 9, 2011 
12 Freedom Riders May 16, 2011