philips came and established philipsburg manor, which, over a number of years, grew to be over 50,000 of land. >> that's more land than the entire city of san francisco! to work such a huge farm required the labors of many different people, including some who didn't have a choice. this was a slave plantation, with 23 enslaved individuals living here. >> that's right. even though phillipsburg manor wasn't in the south, but in new york, it still used slaves. >> slavery was very, very prevalent. in 1750, for example, 20% of the population of new york city was enslaved. >> tenant farmers made up another portion of the work force. >> a tenant farmer is someone who rents land from a landowner, much like a tenant rents an apartment, but in this case, you're renting a farm. in general, they paid their rent with wheat. so they would harvest their wheat, and bring it down to the mill here, to be ground. and a certain portion of that would go to mr. philips. >> and there's one more thing we can learn here. some of the energy sources from our past may be just what we need for our future. >> i thi