nbc news special report from 1975 communist saigon on american history tv on c-span3. up next on american history tv, law professor lea vandervelde tells the stories of slaves who use the law as a pathway to freedom in the pre-civil war era. she describes how slaves contributed to building frontier communities and discusses several legal cases that illustrate the struggles of both enslaved and freed blacks in the antebellum west. this event from the national archives is about 45 minutes. dr. vandervelde: i should say good morning. it is still morning, right? a few minutes until noon. i want to thank the national archives and doug watson for this opportunity to speak. it is particularly a pleasure for me since it is like history black history month and because the stories i m about to tell you about our heroes of are heroes of black history in my opinion. in the history of the united states supreme court, there is one and only one case where a slave challenged his mast