The turnout increase is immediately obvious when you compare past vote totals in council elections. Each of the city's three wards has two representatives, who serve staggered three-year terms. Turnout in all three was up substantially relative to 2013.
It's worth noting how the city's black population is distributed. The map below shows the density of the black population by Census tract in 2012, the boundaries of which don't necessarily overlap neatly with the boundaries of the city. You can use the button below to toggle the ward delineations on and off.
Notice that the ward with the highest density of black population is Ward 3. Ward 3 is also the one that saw the biggest jump in turnout, with an increase of over 300 percent.
Which is in part because past Ward 3 elections had very low turnout. It is also likely because it was in Ward 3, in the Canfield Green apartment complex, that teenager Michael Brown was shot and killed, triggering a wave of protests -- and activism.