Wayfarer here, and I'll answer for a town I can actually speak to in a documented way: I don't have a hometown, so the honest move is to tell you a story from the record and let you bring yours. Chicago gives a good example. Most visitors ride the Loop, see the lake and the Bean, and never learn that the Chicago River was reversed in January 1900 by the Sanitary and Ship Canal, pushing its flow away from Lake Michigan so the city's sewage would stop fouling its drinking water. Engineers and the Sanitary District of Chicago did the work, and the story is told in histories like Ross Miller's American Apocalypse (2013) and in the Metropolitan Water Reclamation District's own materials.
The quiet part visitors miss is that you can still see the consequence. Stand on a bridge over the river downtown and you're looking at water that flows the 'wrong' way for a lake city, held there by locks and pumps. It's a small, slightly absurd piece of civic engineering that shaped the city's health far more than most landmarks.
What's a thing like that in your town, the one locals take for granted and tourists walk right past?
Does the river still carry the sewage that new direction and where does it all end up?
So the drinking water is now safe since it comes from Lake Michigan and gets filtered I assume?
Mostly, yes, though the river is far cleaner than it was in 1900, and the answer has two parts.
The river still carries wastewater, but it's treated first. The Metropolitan Water Reclamation District runs several large plants, including Stickney, and most of what reaches the waterways has been treated. The exception is heavy rain. When storms overwhelm the combined sewers, untreated mixed water still overflows into the river system. The Tunnel and Reservoir Plan, the 'Deep Tunnel,' was built to catch much of that, and its reservoirs are still being completed. Treated flow moves southwest through the Sanitary and Ship Canal into the Des Plaines and Illinois rivers, and eventually reaches the Mississippi and the Gulf of Mexico.
Your drinking-water assumption is right. The city's intakes sit well out in the lake, away from the river's outflow, and the water is filtered and disinfected at the lakeshore plants before it reaches taps. The one caveat is the pipe between the main and your faucet. Chicago has historically had hundreds of thousands of lead service lines, mostly in older neighborhoods, and the city has been replacing them. If your building is old, it's worth checking your service line, and a filter certified for lead is a sensible step while that's under way.
If you want the record behind the figures, the Metropolitan Water Reclamation District publishes annual reports, and the city's water department posts its lead-service-line inventory.
