I've already left some remarks on the previous two episodes so in order to avoid repetition I'll keep this brief.
The series covered London in the 1400s and Paris during the 1700s. This episode begins with the enormous influx of immigrants into New York City in the last half of the 19th century and brings us up to the 21st.
In one year, the population of New York exploded, increasing by about 1,000 percent, if I remember correctly. I wasn't taking notes, except for the fact that in 1890, New York had more than two hundred thousand horses on its streets.
In the beginning, New York City meant mostly the lower half of Manhattan Island. That's where most of the crowding, the tenements, and the filth were. Edgar Allan Poe at the time lived in a semi-rural cottage in Fordham, in the Bronx. The muck was monumental because everyone was responsible for the disposal of his or her own waste. Those two hundred thousand horses alone contributed their share. In the winter, the muck in the streets froze and clogged traffic, until it was about five feet high and had to be shoveled to the side like snow. And when one of those horses died, it was left to rot on the streets.
The episode is a bit different in that it deals with the corrupt politics of the time. Boss Tweed is prominently mentioned. Taxes were collected and much of it kept by those responsible for seeing that they were collected. The equality gap was enormous, and one or two heroes who fought it are described.
Automobiles meant the end of horses, but the beginning of an invisible air pollution. The invention of the chemical refrigerator -- that is, one not operated by natural gas -- led to the release of freon in the air, one of several greenhouse gases now involved in climate change. Of course, no one had predicted this, and yet here we are.
A sewage disposal plant, the kind that processes whatever it is that you flush down the toilet, is described in interesting detail. But, I don't know what's done with the rest of the garbage. Suppose one of the horses pulling those Central Park carriages dies NOW. What happens to the carcass? When I was a kid, we took occasional trips to the beach at Princess Bay on Staten Island. I know what happened to the garbage in those years. It was taken by barge out to sea a few miles and dumped in the ocean. The reason I know this is that the beach at Princess Bay was littered with rotting parts of lambs, goats, and other mammals, gently bobbing in a sea of plastic and metal flotsam, and I asked where the refuse came from.
A final note. You might not want to eat any more sausage after watching this, at least for a while.