Technically it’s a chloropleth of the incidence of slavery in 1860:
I thought I had posted this map several years ago, but I couldn’t find it with the Google.
The most shocking thing for me in looking at this is the minor extent of slavery in Missouri. In a very real sense, the expansion of slavery from Missouri into Kansas was a cause of The Civil War … and yet it just wasn’t that prevalent in Missouri. Perhaps that’s just where the really bad slaveowners congregated.
On the other hand, you can also see why Kansas had so many abolitionists ticked off: you really have to go out of your way to get your slaves up the Mississippi past the Ohio River to get to the Missouri River valley.