I'm surprised at some of the wire hate in here. The show did a great job of having a city be the main character, and they were really ahead of their time in terms of tackling failing institutions (war on drugs, school system, political system, unions, the media, etc.)
They showed urban decay, crime, political greed, institutional failure of our country, and they showed it in a way that didn't really paint people into good-guy or bad-guy boxes. Everyone on the show has shades of grey. Their were honorable people on the the illegal side of things, and crooked people on the legal side of things.
From a practical point of view, the show runners even gave jobs to people that were living the street life to help keep them out of trouble, and help them find other avenues for careers. They really looked out for the people of Baltimore. I was visiting Baltimore a lot at the time it was airing, and I distinctly remember that even though it obviously didn't paint Baltimore as a tourist destination, no one I ever ran into (or read online) seemed (at least back then) to think that the show unfairly represented Baltimore.
It's unquestionably one of the GOAT television shows. So far ahead of its time, and to this day there's never been anything recreated quite like it. It's one of the most ensemble ensemble shows I've ever seen, if that makes any sense.