This is what I gathered from both plantations tours:
* During the Antebellum period, the sugar cane industry down in New Orleans had boomed. The farmers invested in slaves to help them expand their business. Both plantations we visited had roughly 100 slaves in the 1830s. Most of them lived in small slave quarters a short distance away from the main house, but the house slaves lived and worked closer to their masters.
* Among the slaves on the plantation, there existed a hierarchy both depending on their skills and where they came from. The Creole slaves spoke French, and therefore were able to work inside the house and/or communicate with their masters, and therefore were valued more highly (and bought/sold for more money, especially if they were also highly skilled in things like metalsmith). The "American" slaves that were brought in after the Louisiana Purchase were generally valued less, because if they did not happen to speak the same African language as the other Creole slaves, the owners often had trouble communicating with them and they would struggle on the job.
* The slaves worked in grueling conditions, sometimes for up to 16 hours a day. I cannot imagine working in the fields when it was 90 degrees and super humid. I was sweating up a storm just from the short walk in between the buildings during the tour. At one of the plantations, we saw a huge shackle that the slaves would wear around their necks to prevent them from running away.
* The slaves who were considered of least value slept on the floor of their slave quarters, without a bed. Those who were valued more, had more complete furnishing.
* The slaves grew their own foodstuff on the farms, in order to feed themselves and to live off the land.
* During the Postbellum period, the slaves were essentially kept in slavery because each plantation only paid the "freedmen" in tokens that only worked on the plantation, at the plantation store. This way, the freedmen could never really leave because they could not save up money to do so. This continued on one of the plantations until 1900s and on the other all the way until 1940s. The latter plantation, for this reason, still has the original slave quarters that you can visit today. When the current owner bought the plantation in 1940s, the tenement farmers who still lived in those quarters were still largely the descendants of the former slaves. The big difference before- and after- the war was that the freedmen could send their kids to school.
* Both plantations have a list commemorating the slaves who once lived there, first names only (because they didn't have last names as slaves). The slaves were listed with values, some as little as $25 (in the 1830s) and others listed as $1500 if they had specialized skills.
* The tour guide at one of the plantations told us that after the war, the public schools in New Orleans were actually initially desegregated until the Jim Crow laws came into effect in the 1880s. Afterwards, the schools remained segregated until the Civil Rights era. Although I found this article about the re-integration in schools in 1960, the tour guide had explained that the schools weren't integrated here until the 70s. (Anyway, now everyone goes to charter schools in NOLA, and people who could afford it send their kids here to Catholic schools.)
Although I was ambivalent about these trips, and I was bothered by the way one of the plantations seemed to brush the slavery issue under the rug, I still think that going to see a plantation firsthand was a very educational experience. If my students end up learning about slavery this year (and they must, in one of the grades I teach), I could tell them about this experience and when I tell them that people were bought and sold for as little as $25, we could do the math to figure out how little that money is in today's terms.
So, anyway, that was my rumination on math's role in history.
PS. I found this interesting article about Creole slave-owners who were themselves black in Louisiana. It definitely helps to explain some of the things people have said about Creole blacks feeling superior to African-Americans in NOLA. There are lots of numbers in this article to use for calculations of current-day value.
PPS. I've been doing some recreational reading about WWII for my book club, and one of the factoids I learned was that the initial funding for the Manhattan Project was $6000. This was in 1940. This is also a real exponential growth application, to figure out how much that funding would be worth today.